NULLSET  Shoot, what can I say, I'm impressed. I own both VMWare and Parallels (newest versions of each) and VirtualBox appears to be both faster *and* less memory hungry than both of these products. Haven't used VirtualBox extensively yet, but from what I see so far I'm actually looking forward to using Windows occasionally (at least as much as a person *can* look forward to using Windows).  
(Version 3.1.2)

ANDY HEWITT  I feel I have been wasting my money on Fusion and Parallels, having bought both in MU Bundles this year, then having to buy the updates soon after. Getting expensive that is. I only bought VMWare Fusion because of the rave reviews.

Today I've been reinstalling VirtualBox with WinXP, having used it before, and then onto Parallels for a while. There are a few things in the commercial offerings that may benefit some, but not here. Parallels was OK, but for some reason I just couldn't get Fusion to work well at all.

VirtualBox 3.1 is at least as fast as Parallels (a bit faster if anything), and actually a lot faster than a dedicated PC I have here too, and everything I need is working just fine in it. It is a tiny bit more fiddly to get everything working, such as shared folders, but it does all work.

If your needs are modest, don't waste your money on the others, this works OK. Just IMHO of course. Get the demos and decide for yourself.  
(Version 3.1.0)

SURFSPIRIT  Ya This Apps is Great, But Has a Huge Fail! Don't Drag and Drop between the Guest OS and the native one!!!!!!  
(Version 3.0.10)

MAC4DREW  VirtualBox is great. I needed a program that would let me virtualize Windows, so I could run an EXE every now and then. I was tired of installing a trial of Parallels or VMware just to see it expire after a few weeks. And I didn't want to pay for what was entirely a matter of convenience, seeing as how my Mac is perfectly capable of booting Windows on its own. In steps VirtualBox.

I installed Windows XP Service Pack 2 in a virtual machine a few weeks ago, and it's been working flawlessly ever since.

All the standard features you'd expect from a Virtual Machine are there, basic configuration is easy, and the thing is rock-solid.

Perhaps the configuration of the more advanced features could be a little easier, but the documentation for everything is pretty great. If you know what you're doing, you'll be able to get Shared Folders, USB Device Filtering, and loads of other stuff running with just a few clicks.

If you need these advanced features, but you're not super computer-savvy, it may be best to use Parallels or VMware instead. But for everyone else who knows what they're doing, save your $60 and go with VirtualBox.   
(Version 3.0.6)

TECHGEEK  The best virtualization software have ever had!!!!!!!

THE PART WHICH I LIKE THE MOST:-

I COULD PRACTICALLY INSTALL ANY OS INTO THE VIRTUAL DRIVE!!!!

This is I think the best feature I could ever had!!!!

I have installed Xubuntu 9.04 into a 8 GB Virtual Drive and I must say it is great!

It was for the first time I was installing an OS myself!

And when in My Own Computer(The Hos) the net was on I could also access net in Xubuntu 9.04(The Guest)!!!!

So these things make this a superb program if you want to test several Operating Systems!!!!!  
(Version 3.0.2)

PEDRO FARDILHA  If, like me, you use VirtualBox to run Linux or BSD machines you should be aware of a probleml with this 3.0.x series and the guest additions.

IF you have 3D on or you gave more than 64 Mb or ram to the graphic card the GUI will not boot properly.

I've seen this happening with different guest OSs, namely Ubuntu 9.04 (both normal and the new Netbook Remix), CentOS, Debian, etc.  
(Version 3.0.2)

WIZZARD1  The one good file that I did manage to download now works. I have to run the uninstall twice with a reboot in between. I think the uninstall also leaves files behind that don't work with 3.0 as well. As well, it does not install well upgrading 2.2.4. Since the dev does not use standard file locations and 'fixes' some file locations it is probably good to run the uninstall twice with a reboot.

This however does not explain the 400 bad request at 98.53% when attempting to download from their site. Don't think it is an overload situation but a server reboot might clear the issue.  
(Version 3.0)

WIZZARD1  Someone needs to contact whoever posts for download at VirtualBox/Sun. I have been trying to download 3.0 since it was released. Either it downloads and the app will not be start (bounces once) or it will not finish a download - gets to 98.53% and then hits 400 bad requests. I have tried to get ahold of them to make them aware but so far have been unsuccesful.

There is nothing wrong with my connection at all as I have no issues downloading anything else including stuff from Sun and also much larger files. There is nothing blocking this.

Please correct and repost a good build or fix your download servers.  
(Version 3.0)

E_COMMERCE  Still throwing files all over the disk when it has no business doing so.

- "/Library/Extensions" is not a standard location (but at least it's not in /System).

- StartupItems have been deprecated for over four years.

- Mixing in VirtualBox items in /usr/bin instead of /usr/local/bin is annoying.

All of this makes it hard to remove, hard to migrate to a new system, and hard to backup (it you're not running Time Machine). What's annoying is that none of this is necessary - kernel extensions can be dynamically loaded from inside the application bundle, the StartupItem can be changed to a launchd agent and loaded dynamically, and the command line utilities are optional (and could be installed by the app on first run if requested).

All this detrius is unnecessary and sloppy.  
(Version 3.0)

BCWINTERS  I needed to do some work on a Windows-only database, and decided to give VirtualBox a try before shelling out for Fusion. And boy am I glad I did.

This program has a surprisingly terrific level of polish and excellent (if somewhat techy) documentation.

While the UI isn't truly native it's very intuitive and quite nicely finished, and anyway you only touch the UI for a little while when setting up a new guest OS.

I had XP and my development tools installed in less time than it would have taken on a real PC (thanks to disk images instead of CDs!), and only needed to tweak one setting in the prefs to get access to my office's PPTP VPN--I think it was switching the "Attached To" setting to "Bridged" instead of "NAT," IIRC.

From there on out, it was smooth, speedy sailing. I love you, VirtualBox.  
(Version 2.2.4)