An ok game that's worth a play..
Gameplay: It's the basic run and shoot style of gameplay from the console Call of Duty titles, just dumbed down due to the hardware limits the DS has. The game never gets too hard but gets more of the frustrating style. Whenever I get in the mindset to advance there's always something holding me down even more(objective, random enemy with shotgun, confusing level layout).
Graphics: For a DS game it really isn't that bad visually. But no matter how hard you try, at some point there's that thought "Wow, this isn't anywhere near as good as the console version"
Story: The Story in Call of Duty 4: Modern Warfare DS is extremely boring. It's just a bunch of twist and turns that seem expected. When compared to the consoles it's just a sad attempt to bring anything engaging to the player.
Overall: This isn't a game I'd recommend to anyone. If you still haven't gotten around to it, and you just have to because you're an Activision/Call of Duty mega fan then go ahead, go for the gold. It's all that mediocre gameplay you're probably used to.