It says BattleField 2: Modern Combat on the mag I'm pretty sure, but anyhow I use a KB&M on my xbox with the SmartJoy Frag.
you too? heh

The only downside is sometimes vehicular controls are messed up.
For instance in Halo2, driving is HARD using keyboard and mouse based on the systems expectation.
here's a visual.
analog X axis L------------------------[deadzone]----------------------R
when driving if you are going to turn right around, you hold hard L or R on analog and they have an equivilant to mouse-accelleration where you speed up once it's been held for a certain amount of time. (less than a second).
With a mouse, you would just whip it left or right, taking miliseconds. To turn with around while in a vehicle you need to drag the mouse at a decent speed for much longer to get the same turning effect.
Since BF2 plays much like Halo2, I expect the same problems with controls.