A squad-based military shooter is a good idea, but it has its problems. You'll eventually need a long list of orders, and you can only control so many squaddies before things become a confusing morass. The next big revolution in gaming shouldn't be in graphics, collision detection, or level design—it should be in AI, because the stuff they're using to power computer-controlled partners is an outright failure.
So it's really a good idea for Battlefield 2: Modern Combat to allow you to be anywhere and anyone you want to be. You play the game in first-person mode, but if you want to switch from, say, an assault trooper on the ground to a combat engineer on a roof, just look in the other trooper's direction, wait for the cursor over their head to turn white, press the swap button, and, swoosh, you're elsewhere with new stuff.
It works great, but the system ultimately just isn't enough. Enemies like to spawn, respawn, and spawn again, right in your hip pocket, in areas you thought you'd just cleared. Your equipment list is pretty short, and the weapons all feel alike and underpowered. And the vehicles just plain stink. The screen is constantly full of arcade-y glitz, which does nothing for the already-wacky atmosphere provided by the UN Peacekeepers-versus-China-versus-Kazakhstan storyline. Also, there's no body-swapping online, rendering that whole aspect pretty unappealing.
Beyond the game: Battlefield 2: Modern Combat is noteworthy as the only military-themed game of late without a real-world political or military hook, unlike SOCOM: U.S. Navy SEALs, America's Army: Rise Of A Soldier, or Conflict: Global Terror. Please note, however, that it did not escape being saddled with a tension-inducing mid-title colon.
Worth playing for: Soldier-swapping is a great way to get a feel for the entire game map (which is often quite generous), and to do a bit of everything from sniping to demolitions. And if you're playing online and catch someone snipe-camping, you can stab them. Have you noticed that there really isn't enough online stabbing?
Frustration sets in when: The shooting's just okay, the vehicles all handle like drunk pigs, and it all gets old a lot quicker than might be expected. Meanwhile, online play is currently stagnant, with most folks playing the same damn maps over and over, usually as camp-hungry snipers.
Final judgment: This may be the first Battlefield game to come out for consoles, but there are already several PC versions, all quite good. If that's an option for you, by all means, get those instead.