Just got this a couple nights ago and it's pretty decent, way better than part 2. My only gripe is that the sound effects are f*cking impossibly awful, seriously the laser is a just a super high pitched BEEP that goes off every second. Your main gun is a crappy beep too, but it's not nearly as high pitched so you can tune it out after a while. Oh yeah also when your ship blasts into a new level it makes the EXACT sound Mario makes when he jumps.
The levels are pretty cool though, they have a lot of variety. Like level 1 is you orbiting around your mother ship and defending it from attacks, then from there you have fast paced levels, a few vertical scrolling parts here and there, some cool bosses where you have to figure out how to beat them (like one where you have to shoot these balls and make them collide with a weak point), and some really good music. It's not worth $70 but if you can get it for around $40 like I did it's definitely a good game.