I just downloaded the trial...
It's the most boring shooter I've ever played. There's not much action in the initial level, other than trying not to hit the walls, and avoiding the sticky bad guys. It's more of a maze wanderer than shootemup. Yawn.
The graphics are adequate. Good enough, but not spectacular. The music is dull. There isn't much animation. And it's S-L-O-W moving. It won't get your heart pumping. doodlydoodlydoodlydoodly It's worth $3.50 to support gp2x developers, though.
Your mileage may vary. (My favorite shooter this week is Blazing Star for the NeoGeo)
I haven't seen too many really great gp2x games yet. The emulation scene is fantastic, so there's lots of great games from the consoles to play, but the gp2x specific games seem a little weak so far. Am I just looking in the wrong places?
I have a couple of retro-arcade games in the works for the Gp2x. I hope to get the first one out in the next month or so. It should be worth $3.50.