Okay, so I have only been playing the beta for about 3 hours and these are my feeling so far.
Wow! The CoD4 Beta is awesome. I would say that its like a cross between Halo multiplayer and Rainbow 6 multiplayer. Some times the run and gun will work, but its better to be more tactical. The controls feel smooth an respond well. The weapons are awesome and the perk system is a cool new change to customize your solider. Over all the game is a 10.