It's like Enemy Territory Quake Wars, Unreal 2 XMP, BF2142's Titan mode or UT2004's Onslaught mode...but the nodes/points/areas aren't linked so you can go anywhere.
You capture some areas to get water/ground/air vehicles, buy your weapons like in counter-strike, make money, unlock new weapons by accomplishing some objectives and eventually get nuclear weapons to take out the enemy base and win. There's also Deathmatch.
i love the MP, been playing it sence the beta and its great theres still a few balance issues and bugs that will be ironed out in the first patch. and the engine is very mod friendly so even if the stock mp isnt to your liking theres Tons of mods in the works for it already.
There are vehicles at every spawn and weapons facility. You almost never have to run to your next objective. I'd rather run a bit and have some team play than just have team deathmatch the whole time. Sure its opinion, but for teamplay, Crysis is infinitely more fun. COD4 has no emphasis on teamplay, even in the objective maps. Sure you can try and coordinate, but its always up to the last person standing to complete the objective.