Op Flash 2 will be dumbed down to fcuk, purely because it is a multi format release. The original was class and very realistic, but you needed a keyboard overlay to be able to coordinate Commands and what not. How the hell they will be able to apply that convincingly to 8/10 Xbox buttons is beyond me. Yet again, cynical cashing in rather than holding their hands up and saying 'this should be a PC only title'.
The main trailer is all in-game footage (though probably on a better PC than this). I believe the only exception is the scene with the flashbangs which is using custom animations for a cutscene (though it's still the game engine).
The campaign is reputed to be good but jewel in the crown is the editor - a 225km^2 sand table to play with.
For those that don't know the heritage, BIS own the technology from the original Operation Flashpoint, Codemasters only own the name. ArmA2 is a development of the OFP engine. Codemasters have had to build OFPR from scratch; not necessarily a bad thing but I won't be preordering OFPR like I will ArmA2.
PS. OFP/ArMA/ArmA2 are parallel developments of VBS2 which is used as a, er, fight sim.