I got a really nice first impression from this game. Especially because of the controls, but also because of the overall feel of the game, the way you have put the graphics together have made a nice style for this game. The menu with the cursor changing into a hand, and the text fading is also a nice touch.
The way that the asteroids blow up, is realy nice, and leaves you with the feeling that you just want to shot one more. And since this game is about blowing asteroids up, this makes it into one of the best asteroids like game I have tried.
One other thing, which makes this game stand a bit out from many other asteroids 'remakes' is the ability to actually set the weapons to use for primary and secondary fire. This is a really nice feature, which lets you play the game in different styles. Nice!
Ah! One last thing before i mention the one bad thing i noticed: Thank you for making this game run(And it ran normal!, not slow, or with any real slow downs at all) on my old computer, with 1.5ghz and a Nvidia GForce 2.! Hehe.
So i bet your programming skills are good. (Don't know if you really gave speed a consideration though but anyway. nicely done! )
The one 'bad' thing i noticed:
After blowing up an asteroid, its 'fragments' starts moving very diagonal / in very straight lines, and maby a bit to fast, fix this and i will think of this game as beeing perfect for what it tries to be.
Sry. For my bad English, but my danish writing skills are not any better so

.
Yup, thats it.
Nice done Jimpo.