With the patch to 1.05 from 1.02, one is now able to set enemy AI to expert while in the easy mode of the difficulty settings. (I just need unlimited saves so I play in easy mode and try to simulate the more difficult aspects of expert mode.)
With the Enemy AI set to expert, it's a whole new game in my opinion. Enemies are much more aggressive. They will flank much more forcefully.
I guess what I value in a shooter game is loosing the sense during gameplay that it's a shooter game, and feeling instead that I am out their on the ground trying to stay alive from these people who want to put me under.
I can't claim that every mission does this for me, but the 1.05 enemy movement often results in a "suspension of disbelief".
By the way, I did not see any loss of smoothness going from 1.02 to 1.05. (7600GT, 2.4 P-4, 1 Gig Ram). I love playing without the grass, it makes missions much more doable.
Just my thoughts,