I find myself overusing the gun and I think something should be done to make it not so temping. I have a few suggestions on how this might be accomplished. First, either penalize the player for shots that don't hit via a point deduction or award an accuracy bonus at the end of each wave. The bonus might even be tiered such that if you have over 50% accuracy, you get X amount of points, over 75, you get that multiplied by 1.5 then over 90% and it goes even higher.
The second might be gun overheating if used too much. This would mean that you'd have to start doing some evasive flying to try to stay alive if this happens. It would ramp up the difficulty when you feel hemmed in by roids all around you as you couldn't just shoot your way out. You'd either have to find a path out of the center of it while you wait for your gun to cool down, or use the hyperjump and risk ending up on top of one.