This is one of my favorite racing genres so Starship Racers has me interested. The game has a lot of potential, but honestly, it needs a lot of work. I don't mean to be critical, but I just want to point out the issues I saw and offer some advice.
The races run too long, so the experience feels tedious, especially since there isn't a whole lot going on. It wasn't clear what lap I was on; the HUD was saying one thing, the track sign said another, and I'm pretty sure the race ended on lap 4 of 5. When the race ended I was just dumped onto a results screen with no indication the race was over, that I had one or anything.
I can't really speak to the AI and it's quality. They didn't seem to pose much of a challenge and mostly appeared to be shooting at random. I never really felt like I was racing them, they were just there.
Maybe the option exists and I missed it, but I suggest a third person view. If anything, for this kind of game I think it should be the default. There should also be a position indicator, and some kind of warning when an enemy is right behind you so that you know when to take evasive maneuvers. Targeting also need to be improved, I could never tell when my weapons were lined up with the enemy, nor if a hit connected.
From an aesthetic standpoint I think the ships should look like they're floating above the track instead of skating along like they're on ice. I recommend giving your vehicles more mass. Currently they look like flat boards, so they're not very interesting to look at. When firing a weapon it looks like the beams will fly right over those ships. Look at WipeOut. Maybe it changes on other courses, but I think the edges of the tracks feature hard barriers. If you're going to do the half-pipe approach then your vehicle shouldn't slow down if you go up the sides. Look at Stun Runner for an old school example of this kind of gameplay If it does slow down your vehicle there should be obvious indications on the course where it happens, like the odd road patches in F-Zero.
I also suggest looking at Repulze for iOS. That game was released last year and they did a great job with it. I'm not suggesting you copy these guys at all, but do the research. These games all do things right in their own unique way. Part of what makes those games fun is the drama, the way the ships move, the excitement of trying to pass a competitor, of shooting and being shot at.
It's the small details that enhance the experience. Take WipeOut HD, look at how the camera pans around the ships at the start of the race, the way they hover, the glow of the jet engines, stuff like that. It's a ton of work, but all these things need to come together for a game to really work.