The most notable difference between the three operating systems are these:
Mac OS X - cost = buy a Mac $1200, the Mac OS X only works on Apple computers. It's a really pretty and fun system to work in. Hardly any support for computer games.
Windows Vista - cost $300, works on most computers, has bugs and security flaws, plays tons of games, and "just works".
Ubuntu Linux - cost $0, works on most computers, can run windows software and "just works" (usually)
That said, I've been messing around on Ubuntu Linux (version Feisty Fawn) and I think it's a great. It's not quite as easy to install programs as Windows and it can be tricky to set up, but I think most people could do pretty well using this version of Linux. At this point, Linux can now be used by 2 our of 3 types of people (as opposed to the 1 type about 2 years ago). The two types are 1) People who never download new programs or try to install anything new and 2) People who are pretty knowledgeable with computer software / programming.
I don't recommend it to people who don't have high speed internet access or anyone who doesn't have a computer expert nearby to help with problems.
It's got some really great, free programs though. GIMP is an image editor that is really robust and comparable to Adobe Photoshop (a very expensive program). OpenOffice.org is the equivalent to MS Office (another very expensive program). It comes with Firefox as an internet browser and Evolution for e-mail and calendar stuff. It has GAIM for instant messaging that allows you to talk with people in all other messenger applications (MS Messenger / Yahoo IM/ AOL instant messenger).
K3B will burn CDs and DVDs. Rythmbox will play all your audio files.
Best of all, it's all free.
Now for the fun part. I installed Beryl (an awesome desktop application that lets me do this.
Four Desktops (Windows only has one) / Rotate a cube to see and use them

Windows don't just close when you click the little red X to close the window, they go up in flames now :)

Thumbnail views of your minimized windows before you maximize them

A window manager called "slam"...bump your mouse cursor up against the top right corner of the screen and Beryl will display all your windows in an easy page (below) so you can select the one you want to use

A nifty little feature called peek allows you to peer underneath a window you are currently working in. Also notice when you do that, it makes the window slightly transparent.

Last but not least, the Jello effect when you drag windows around the screen they stretch, then snap into place.
You can turn all these features off or install many more, it's all up to you.
If you want to give Ubuntu a try, just let me know :)


