Orgasmic!
Okay, this game is awesome on so many levels I'm not even going to try to list most of them. Instead, here's some things that stood out to me:
-Particles/effects: Normally, I find an overabundance of particles somewhat annoying, but in this case, it's an integral part of the feel of this game. The lasers darting across the screen, the beautiful explosions, and the screen jiggles all sucked me into this, better than most games of this genre have done.
-A.I. I loved the enemies would branch off from attacking your base and trail you, only to split off to their original target. Also, the enemy seemed to up it's game as you advanced in powers, which leads me to -
-Upgrades: I only completed the game once, I didn't get to see all the power-ups. But from what I've seen, I was impressed. Also, the fact that you constantly had to keep upgrading added an element of strategy, which complimented the already badass gameplay.
Honestly, this game was pretty epic. It felt like I was playing out a space battle scene in Star Wars.
Keep it up!
P.S. If you make a sequel, which you should, I think it would be a pretty awesome idea if you re-engineered the gameplay so that you could alternate between your teammates ships, and put less emphasis on a lone ship, and more on massive battles.