A good game with some flaws...
There are some nice weapons like the M16 you start out with and the AK47 from those regulars you meet almost throughout the game. Just like any other Call of Duty game, you can pick up a maximum of two weapons of your choice.
Missions are fairly easy (i've only played on regular) while you switch between a US Marine to a British SAS. The switch are a bit sudden, however, for you take a role as random soldiers (with are nameless) throughout each mission. They've done a excellent job as to what needs to be played, like infiltrating a science building, to covering a group of US forces with a Blackhawk.
For me, the only fun in this is gunning people on a blackhawk because that's the only unique thing you'll find in a DS FPS. I also play that because going mobile is a bit tedious for you do the simple run and gun.
Despite all these goods, there are some down sides to make this game a 10 out of 10.
1) There are absolutely NO re-loading animations in the game.
2) Allies are retarded, they just stand right in the middle of the fight and get killed.
3) Unlike the rest of the Call of Duty series, when an ally dies, YOU ARE ON YOUR OWN.
4) Switches between soldiers are very sudden, be ALERT.
5) Enemies pop out of every possible corner, always look left to right, then back.
6) Most maps are very clustered (no running space).
On the other hand, there are good things about this game:
1) Weapon and character models are very well done, looks realistic.
2) Sounds and ambient and music gives the game an extra boost of excitement.
3) You use almost every modern weapon/vehicle we have nowadays.
4) People actually talk on the radio and call for you, etc.
5) Defusing and setting a C4 takes patience, makes you use your brain for once!
6) Melee very, very well done (feels like they spent more time on this than on reloading)
Overall, it's an excellent game. It is absolutely not a disappointment. Once you pick it up and play it, you never want to put it down.