I liked that the game doesn’t let you shoot endlessly, so you have to think about where and when to fire a projectile. The randomness created interesting situations, and a couple of times it even made me a bit nervous.
As for the downsides, I’d highlight the following:
Scoring isn’t very engaging, and because of the unpredictability of bonuses, it feels like achieving a high score can be quite difficult (although for some players this might actually be a plus).
Also, the shooting sound is very irritating in cases where you need to fire a huge number of shots, like when destroying a large ship. I’d prefer if the sound varied or at least had randomized pitch.