Although there are glitches in some missions, once you've learnt how to play the game well, the only thing that can stop you are your mistakes. So your Team doesn't return fire when attacked. This is good on some missions, though, where you aren't allowed to kill anyone.
The missions get progressivly harder and although the third or fouth might 'seem' hard when you first play it, the game has a lot more to offer.

With spectacular backgrounds, you can visit a lot of places. I just might ask, cutscenes???? Also the graphics could be better when you zoom out to get a better look around you.