STEVEN GOODHEART  I just downloaded and installed the Snow Leopard beta, and -- woo hoo! -- I've got MailTags back! After a morning of testing, I haven't run into any serious problems...To Dos I create in MT are showing up right away in BusyCal (BusyCal is one of my favorite new programs -- think of it as iCal Pro) and tagging seems to be just fine.

Given the intelligent and cautious install instructions and caveats at the website and with the installer itself, no doubt this is a beta, but I have to say it's looking pretty darn good at this point. One thing I did do was to run the uninstaller before I did a fresh install of the Snow Leopard version, just to be safe and remove any pre-SL cruftiness.

Looks like MT is getting a significant facelift/reworking because of Snow Leopard, so though I've missed using it for a while, I'm really glad, in the end, for the change. I think we'll end up with an even better, stronger program. But for now, the main thing is that this is a workable version for Snow Leopard users, or at least, for this SL user. My two bits.  
(Version 2.3.1)

XPLICIT  This app would have been quite a good extension to Apple Mail, but it's not. It's really buggy:

"Keywords -> Add to preferences" doesn't add the keywords to preferences, deleting keywords doesn't work at all, keywords suddenly disappear from the list, "Add keyword" adds new keyword more than once, etc..

If you need an app like this to work with ... forget this one ... at least for the moment.  
(Version 2.3)

ANON BUD  I cannot wait til the final Snow Leopard version comes out. I tried the beta for a bit, but it didn't play nicely with mail.app at all: messages not rendering, keywords lost, crashing, etc.

This is a fabulous app and I miss it terribly! Please InDevÂ…hurry up with 3.0 final!  
(Version 2.3)

SHOCKERSPAZ  Im sorry, today of all days, to release a new version and state "10.5 and later, Mail 3.0 or later" is a blatant lie! It does NOT work with 10.6 nor Mail 4.0!  
(Version 2.3)

RARO  Actually a great app indeed. I have used it extensively. But after a while, I wasn't able to access certain Mailboxes anymore. The only measure that helped was to disable MailTags.   
(Version 2.2.3)

EJI  Looks like it conflicts with WideMail v.51. The Mail.app message window won't open, and if you manually select it from the Window category in the menubar, it brings up one messy mail interface. Crap.  
(Version 2.2.2)

MALISTA  I've been using MailTags since day 1, looking for an alternative to Entourage which had better features at the time.

MailTags saved Mail for me, no less!

its free working sibling must be mentioned: Act-on.

bring QuickSilver in the equation, and your workflow becomes seemless.

highly recommended.  
(Version 2.2.1)

ONEBLESSEDGUY  I don't understand the review below. I have installed it and it works great. Perhaps there is an incompatibility with another plug-in that the reviewer has installed.

At any rate, I wanted to post something that states how much this program has already helped me and I've only been using it about 2 weeks! First, because I was using Mail Act-on, this program was easy to implement b/c I already had many rules set up. I was able to adjust my rules to include mail tags and get even better filtering and email flowthrough!

Second, b/c of mailtags I was able to implement a GTD workflow of my emails that has left my inbox empty and my to-dos organized. I actually enjoy it when I get an email b/c I get to organize it away. I'm ready to handle more than I feel like I ever have been.

Third, the hardest thing to do was to set up what I wanted in a workflow, did I want to use a Today, Tomorrow, Next Week, This Month kind of smart folder and file accordingly or did I want to use a color system with colors changing as the day approached. Almost anything is possible with MailTags.

Try it out! I don't know what I did with my emails before I did this. But I know I wasn't as efficient as I am now.  
(Version 2.2.1)

EGN  This is definitely not there yet. Just messed up the messages that I tagged. Could not drag them to any of my forlders; they just popped back in to the orginal folder. Not even after deinstalling. I had to delete the messages to get them off. Anything MT touched it messed up. All the other emails that I did not tag with it were OK. So it's off my Mac. This is the 2nd time I've tried to use it and the second time it does something I don't like. !  
(Version 2.2pb5)

BLLOYD  This mail plug-in has been fantastically useful for me. I'm not using all of the functionality, but rather just adding tags to messages (waiting, follow-up, etc.) and using the OmniFocus plug-in so I can quickly move to-do items as follow-ups over there where I manage them in a centralized location.

I tried to work with Leopard's to do functionality but it had some real limitations which made it unusable for me (specifically, if you have a few hundred to-do items over the course of all time with Leopard, which I did, it breaks down).

The developer has been fantastic in quickly resolving issues, and in adding much needed functionality. This is a core productivity application for me, along with OmniFocus and Circus Ponies Notebook I can efficiently keep track of whatever I need to, and follow up in a timely manner. Nothing falls through the cracks anymore.  
(Version 2.2b24)