Well I picked it up today and its pretty much exactly what I expected and hoped it would be. It starts off simple and relatively easy then it ramps up gradually as your progress through each stage. The stages each has a boss and they are inventive in the ways you fight them. Ive gotten down the flow of the game for the most part. Basically your aiming to kill enemies of the same color in a row, if you kill 4 like colored enemies they will drop a weapon power up that will last you about 10 seconds, each color has its own type of weapon power-up but they are all pretty useful, you easily take out formations of guys with these weapons. So the goal is to keep a chain going by killing enemies of similar color in packs as they will keep dropping weapon power-ups, and you then can get a chain going scoring more points. There are UFO enemies that will hover across the screen, some of those will activate bonus rounds or other random bonuses. If you complete a bonus round you will go into fever mode which ramps up your ship with a really powerful gun so it becomes an all out shoot fest.
Its pretty freakin addicting, theres all kinds of various invader enemies the game throws at you, ones with shields, some with quick movement behaviors, some with powerful weapons. It keeps you on your toes and even when you hit a game over screen you cant help but want to try again and keep playing to get further. Plus the game is retailing for only 20 bucks, which is more than worth it.