This is really a lot of fun to play. I'm generally opposed to leveling systems in shooters (like COD/BFBC) but it just works here. I'm a huge L4D/L4D2 fan and this is right up there in fun factor though I'm not sure it has the same replay value.
Anyone else think this may be Valve's entrance into the 'free to play' game market? The levels included are relatively short and can be completed on normal or hard pretty quickly. I could see them releasing more levels/classes/weapons/achievements for money. Of course people are going to make good levels with the already released SDK, but Valve is up to something here. That something is probably micro transactions for additional game content once people are sold on the core game. I bet it's also a good way to get more people to try and use Steam.
Demon's Souls Official Thread | Currently playing: Left 4 Dead 2, LittleBigPlanet 2, Magicka