I first heard of this game following it's progress along with the Orange Box. I was more interested in Portal in all honesty, but I'm not the biggest FPS fan so I wasn't going to bother purchasing the game. I ended up playing it at my friends house a few times and it finally sank in. What a game.
So I bought the game and sat down to play it. I use a low-end laptop so my settings are low, even so, the level of detail is fantastic. The game comes with 10 maps at the moment, but with so many user created maps, you should hardly be bored.
Gameplay wise, the game is near flawless, simple WASD controls work fine and having the 'Call for Medic' on E is extremely convenient. There are several commands bound to Z,X and C which all serve their purpose and a taunt feature bound to F. The taunt feature has some amazing taunts and the animations overall are amazing. If I had one complaint it would be the unpredictable critical hit system (albeit with the Sniper Rifle, Headshot = Critical Hit) where one Crit can ruin a kill streak in a heartbeat.
With 9 classes, each having their advantages and disadvantages against each other there is so much depth to each one. The models are all distinguishable and each has weapons tailor-made for them. For instance, the brute force Heavy swings around a bulky Minigun, while the zippy Scout carries a Scattergun capable of spraying bullets in all directions quickly.
With the new weapons being revealed for each class, the content is simply astounding, and there are still 7 more classes to have the treatment. Put it this way, GET TEAM FORTRESS 2