WYNLYNDD  Jaikoz is an excellent id3 tagger and has helped me "save" my collection as poorly tagged songs made it difficult to find anything. The developer is rather responsive on his forums and often updates his wishlist and buglist to let you know where his priorities are at the moment.

In addition to cleaning up tags, it adds album art and lyrics, and can help dedupe your collection. Yes it can be a bit slow, but some of that slowness is the limitations of the MusicDNS servers that it uses to help identify songs. (they have a throttled limit of 1 song/second plus, the server is often busy causing Jaikoz to retry a few times to ensure it gets the information)

I concede that it can be difficult to load entire collections at once, especially as people's collections get so huge. (we are now what 11 years into the mp3 revolution?) However, it has improved and should keep improving (I can now get about 15K-20K loaded at once).

One of the best $22 I ever spent.  
(Version 3.0)

1CHARMEDLIFE  This is a great tool for managing large collections and their associated metadata. We have over 26,000 songs in our library and this did a great job allowing us to manage the tags.

The only drawback I've had with it is that it seems to embed multiple versions of album artwork with the files. It would also be really helpful to be able to tell the software to *not* fetch artwork under a certain size. (It stinks to have an awesome interface up on a big flat screen, and it's scaling 112x112 images up to fill a 50" screen... and weeding those all out by hand takes forever).

End to end though, this a great software and I highly recommend buying it if you have a large collection to manage.

(One other note, with really large collections, you have to process them in chunks unless you have tons of RAM. We have 4gb on the machine we used for this, and we could still only process around 10,000 songs in one batch... )  
(Version 2.8.1)

LIAM_IMAC  It works well at times but it is very slow app. it takes 30 secs or more to start and its not the most responsive app when running.  
(Version 2.8)

CFSCHOLL  The application works but you can't have your itunes open while changing your song information. I adjusted the tags of a song I was playing and itunes crashed. Afterwards it indicated that my files could not be found anymore so I had to find them in the itunes folder. The name of the artist had changed so I guess that is the reason why itunes thought they were deleted. The solution was easy I just added this folder again to the itunes and now they had the correct song information. As this is a 30$ application I would expect that the integration with itunes would be better. As for what others said about the speed its indeed not a problem.   
(Version 2.8)

THEBRIX2008  Having tried all the other (non-iTunes) taggers, Jaikoz wins. The only real downsides are the UI appearance - but that is a price worth paying for a cross-platform application - and some aspects of usability, as it is possible to cram up to four extremely "busy" panes (catalogue, tracks being viewed, tracks being edited, exhaustive details about the current track) into one window.

The most useful feature of all is that it is extremely easy to cut and paste information between tracks, as the track editing pane is spreadsheet-like. It is incredible that no other Mac application (that I have come across) has adopted this approach as it is by far the slickest when working with complex albums. The other big win is that, in effect, any field, including filenames, can be set automatically from the (parts of) any other field using macros: for quick cleanups (e.g. the common one I find where composer and artist are reversed) this approach is unbeatable. Finally, there is standards support for ID3 tags of every version; tags set in the iTunes view are automatically copied to the ID3 view so that any quirks, because of differences between the standards, can be ironed out on the spot. If you don't need it the ID3 view can be switched off.

And the MusicBrainz facilities work superbly; although I have less need of it than most (as I mainly listen to classical music) they fixed several "unknown" albums handily.

As others point out, this application is not meant for an existing, perfectly-tagged iTunes collection which will only ever be used on a Mac and an iPod; it is perfect for building a collection which is not tied to Apple products.  
(Version 2.8)

87BOOSTED  Jaikoz Review:

First off, to those criticizing Java as a language choice. I mainly address this as the reviews that are most biased seem to use this as their main bias. Ignore them. Java is by no means as fast as C, C++ or a host of other languages out there, but this programs purpose is not limited by speed. I can tag 25k mp3's at a time, and do more if I so desire as Jaikoz is not limited by Java but by the hardware you own. You can run it on close to nothing if you take your time. Secondly Itunes is an AWFUL program for large music collection. Smart execution for selling music tagged by apple, not so good when you have a large dissorganized mess from years of ripping and collecting. With Jaikoz you can turn music organization into a hobby and take some control over your collection. I use a celeron single core and 2 gigs of ram shared across multiple computers, I then tag using remote desktop to this computer. I use itunes to load my ipod via this shared drive, no bonjour only simple folder structure and drag and drop. This keeps my main laptop free while jaikoz works. The main strength of this program is support, ask and the main developer responds, if it is feasable it will be released. Tagging music is useful for collectors and enthusiasts alike. Itunes is great for small collection bought from apple. One final word. I had a small collection seperated of several gigs from years ago, all the music was tagged by numbers and no artist or data to relate anything about the music. I could have listened for hours and MANUALLY tagged it. Jaikoz actually attained the music ID's and tagged MOST of it. ALl the music was from a drive I recovered after it crashed for some unknown reason. Ohh and the best part. Free updates for LIFE. It is a shame that there are negative reviews by folks who have little understanding of the product. This is not for 100 mp3's that already are tagged. This is for the enthusiast that is interested in building or maintaining his/her collection. Thanks Jaikoz.  
(Version 2.5)

MADMACMAD  Well i had a Problem:

i got more than 300 MP3 wrong Tagged... befor every ID3 Song Name was a Numer like 01 - and the Year for the Album Name. So i tried all ID3 Tools availible by Macupdate like: Dukko, Musorg, ID3 Editor, ID3Mod, a better Finder rename; iTunify, MPFreaker and Jaikoz.

Jaikoz was the ONLY tool who did the Job in Batch Modus!!!!

forget all other Tools ....waste of Time

This is the only one you need for all Actions I#m shure afetr a few test !!!!! Don't waste your time !!! Try it i highly recommend this Tool !!!!

Thank you Developer it's really worth the 30$ for this compared to the other Tools.  
(Version 2.5)

FOCHER  It's a fair criticism that this application does not have a user interface that lives up to what you expect from an OS X app, but that is the limits of a fair criticism for Jaikoz - and mostly due to its use of the Java user interface libraries to keep it multiplatform.

First, there is almost no other tagging application on either Windows or Mac (and this one also works on Linux) that has the feature set of Jaikoz. The UI sometimes gets in the way of understanding the power of it, but Jaikoz definitely has power.

Second, you have nothing to lose by trying it for a bit with the trial download. For anyone with a large music library that wants to clean it up with a) proper tags, b) proper artwork, and c) using acoustic fingerprinting to track the metadata then Jaikoz is for you.

It uses MusicIP acoustic fingerprints to automatically identify an audio track and then the Musicbrainz public "social networking" database to match the acoustic fingerprint with the metadata.

Speed is also not an issue, so don't let the "Java" mislead you. It's very fast at performing the acoustic fingerprinting and retrieving the metadata. Just try it.  
(Version 2.4.1)

XPLICIT  Looks and feels to me like an OS9 program. And its usability s**ks.  
(Version 2.4)

BLUECAT  Good solution to correcting lots of meta data

If you have songs with missing or incorrect meta data on your Macintosh, Jaikoz is well worth your time and money. There is no other program available on the Mac that provides all the capabilities of Jaikoz.

If some of your meta data is correct, you can easily transfer the correct portions to other songs that have problems. The color coding scheme showing what data has changed is very useful, and allows you to easily verify the updates before you save them to your hard disk.

Jaikoz integrates with MusicBrainz, giving you a chance to capture a lot of meta data starting with just the music, by matching up the song and grabbing the meta data from MusicBrainz.

Jaikoz can grab album artwork and song lyrics from the Internet, for all of your music, with one command, and store the data inside your MP3 file.

Jaikoz has extensive documentation explaining each of the features available, and suggesting sequences of operations to perform for best results.

The author is extremely helpful with support, and releases new versions with new features on a monthly or better basis.

The downside to this program is that it's written in Java, and does not have the good looking, fun to use interface that Mac Cocoa programs have. Although an MP3 tagger program is not something I use on a daily basis, so I'm willing to live with this.  
(Version 2.3.1)