I like the style, which as Doomhammr said, reminds me of Raptor. The ship graphics are well done, and although the ground installments are of much lower quality, they're nice (wish they were destructible like in Raptor)
I liked the weapon upgrades (the missiles are a nice touch), but by the beginning of the second level I've already reached the top option - that removes a lot of the incentive to continue for me.
Rescuing the colonists is nice, but notice that it's possible to beat the bosses before reaching all of them. I killed the second boss a few seconds after collecting the last colonist (without even using the super weapon), and killed the third boss before all the colonists were reachable.
The action was slow paced for me (even on low quality), and the enemies were too far between for my taste.
It's good that when you die you can retain a few of the upgrades. I dislike games that force you to begin from scratch.
After the third boss I quit the game - I've felt that I've seen all the game has to offer, and was mostly put off by not being able to further upgrade the weapons.