Team Fortress 2 Classes
The nine classes in Team Fortress 2 have been balanced down to a T (indeed Valve is still balancing out some classes before its official release next week). Each class is deadly on its own but one of the big reasons why the game is so fun is that it encourages true team play. Having a medic heal up a Heavy Weapons Guy as he charges into a battle is a common team up, as is teaming up a Demoman with some of the constructs of the Engineer to defend a base. One of the big problems with the "support" classes in any team-based FPS is that they aren't really all that fun to play, but playing as the Medic, Spy and Engineer in the new Team Fortress 2 eliminates that issue. There's nothing quite like stabbing an enemy while playing as a disguised spy or getting a feeling of satisfaction as your machine gun turrets take out a slew of bad guys. Protecting a fellow teammate as the Medic is also a cool feeling.
That's not to say that playing the offensive and defensive classes aren't enjoyable. Firing the big mini-gun on the Heavy Weapons Guy or blowing apart enemy teammates with the Soldier's rocket gun has that visceral effect that you would expect. The Demoman can fling grenades with ease and the Pyroman's flame thrower can be quite deadly in close quarters. The Sniper is still a class of patience and skill and is for those players who just need to watch and wait. We still aren't that crazy about the Scout class; yes, it's fast moving but in our playtime we found it was the hardest to use in terms of killing foes.
Valve has decided to only release six maps for the initial version of Team Fortress 2 but as the developers state in the audio commentary portion of the game (a must if you have any interest at all in multiplayer game design), they would rather make six really great map rather than, say, 20 maps of which only a few might get played with any great frequency. The maps of Team Fortress 2 might not be the massive maps of, say, a Battlefield game, but its clear that the level design has been created to make players think about strategy; where bottlenecks are, where to defend and where to attack. This is not an attempt to make a level that is a "realistic" setting but one that is designed for fun gameplay (Valve does plan to release additional maps for Team Fortress 2 in the coming months).