The balance between classes is very good. Maps are easy to discuss and identify. Requires team work and communication.
As mentioned the xbox version is mostly made up of 200 people or something... it's a very small community there.
The pc version has more maps, better graphics, and more weapons.
Also it's not a conventional FPS. The only class that I can think of that has a sniper rifle + a gun that shoots bullets that actually go straight [uneffected by gravity etc] is the sniper. It's the only class thats mechanics resemble a typical FPS. The rest are all doing other things, using shot guns, using flame throwers, lobbing grenades, building sentries, back stabbing, shooting rockets, etc.
Each class has a powerful strength and if you know how to use it you will really kick ass. You should google tf2 classes and see what comes up and check some youtube videos.