Contra 4 is definitely worth it, however, it makes heave use of the dual screens and it has never left the DS platform. However, the gane looks and plays great, plenty od challenge missions and unlockables. If you can play it on a DSi XL it is even better.

I was thinking the helicopter crash scene would lead to a mid boss or some other thing in the final game.The boss animations are like that in contra 3, 4 and hard corps so those are probably tjere to stay.