Omega Five is the Coors Light of shmups. Great taste, and way, way less filling.
The problem is that there just isn't much there. Four levels with as many boss fights (two of which are just mind-numbingly easy) just isn't enough to keep this game in the "buy" category. Even two of the characters are near palette swaps. It has its heart in the right place, but it simply doesn't give enough to warrant a permament place on your 360's hard drive.
Unless you absolutely have to play every shmup that comes out, play the free demo (a full 1/4th of the game) and pocket the $10 towards more long-term endeavors, like Rez or Ikaruga. Pity too, three more levels and this would've been a classic.