I really like these kinds of arcade-y shoot'em ups that allow you to strengthen your character as you play. This one is quite fun, has 4 characters to choose from with different abilities that change things up quite a bit. It's got a good difficulty curve.

However, on XBox at least, it has atrocious load times and often fails to save your progress. I'd buy a new skill in one play session, come back a few days later and no longer had that skill. Completing one difficulty level opens up the next. When I finished Normal mode, Veteran mode opened up. But then the game crashed and when I relaunched it, Veteran mode was no longer open to me (also I never got the achievement). I had to go through it again before it worked properly. Then I finished Veteran mode and same thing happened. Also, if you use the XBox home button while playing, the controller will stop controlling the game. A shame, because this was fun when it was working.