Picked up N+ for the DS yesterday. It's quite challenging, but if you just keep at it actually fairly easy to get through. Anyone who's played the Flash version of N knows what I mean. And if you haven't then you should.
I also picked up Red Faction: Guerrilla the other day. It's fun, but sometimes it seems you die when you shouldn't when other times you're practically invincible. It does a good job of situating everything, but I would have liked to see the game world a little fuller, with more destructible things in it.