Finished yesterday: a good game indded, but I've a few remarks.
Pros: excellent graphics on a DS, good level design (though a bit repetitive, but it's not so easy to be original in an FPS), the droide.
Cons: I must say the story is really engaging during the first missions, then it becames just an excuse to go on and fire at the ugly aliens (some good ideas of the first missions, like the driving sessions, have been forgotten too early)
I've found some bugs: the game froze during some cutscence or after having read a log from a terminal (I had to switch the DS off and switch it on again), during the last boss fight I fell, while walking backwards, from an open "window" of the room and I found myself falling in a sort of green sea.
I've also found that the firing rate drops during some fights with many enemies in the room! This is a serious issue, as this happens exactly when your weapon must be reliable.
WARNING: SPOILERS AHEAD !!!
It's clear the developers wanted to do something reminding Halo: the settings, the vehicle, the first weapon you use, even the last sentence during the last cutscene "I think this is only the beginning" (or something like that).
But the whole story behind the firings is without any twist: you go on, kill everybody until you kill the evil alien master.
The last 2 missions are, in fact, the most disappointing: how can you pretend to go in another world, landing with your ship so close to you last objective position, cover by feet only a "tunnel" with the same kind of enemies you've found during the game, and find the last boss after so few minutes ?
I think that the whole "alien world affair" should have been better developed to give the game a more compelling end.
By the way: who is the "unknown source" who guides you to the end ? Is he the "Prof. Mattheus" (or something like that) who explored the whole facility before you and left some logs in the system? I don't remember any explanation about this.
END OF SPOILERS
To sum up: a technically very good game for the DS, but it should have been a great game with a better story.