Wow, I'm impressed. I have a soft spot for Solar Striker so I'm liking this very much.
Played Easy only once or twice, but the Hard mode...very fun. I had difficulties just getting past the first boss until I ran the text.exe, the one without sync (didn't experience any technical hiccups, either), and then I got to Stage 4's boss thanks to the steady framerate. Oddly the Stage 2 boss feels a lot easier than the Stage 1 boss, mainly because taking out the destroyable parts doesn't result in a different kind of firepower being thrown at you, unlike with the first boss. Plus the first boss' patterns are more tight and harder to squeeze through.
Stage 3 boss' second form is highly annoying thanks to the ship's narrow firing arc. It's doable, but tricky. The last form was considerably easier (but looked cooler

).
The way you updated the bosses is very cool - they're easily recognizable from their GB ancestors, but the new attacks and destroyable parts make them feel totally fresh.
Few quirks: I didn't feel any difference between "Accurate" and "Fast" control. The ability to speed up or skip the score count at the end of stage or death would be appreciated. Also it would be nice to be able to enter one's name via the keyboard or a screen with all the available characters visible.
Definately looking forward to the completed game.