I was almost sold...
I lasted much longer than I expected (due to earlier reviews), but it was just not as good as it could have been. I was really excited once the meteor showers started coming from two directions, as the earlier meteor shower levels were just tedium. However, what made this game not good for me was when after the manta ray alien swarm, the game saw fit to leave me with one bar of health, and with no health or shield power-ups. Needless to say, the aliens that shot 6 balls in a ring killed me quite quickly.
Also, the lack of any boss fights detracted from the score.