I find Cybercore pretty damn tough in places, due to the brutally stingy powerup system.
When you have nothing but a peashooter, I find that increasing your speed (and basing your strategy on swift dodging) really helps. And, not just for Cybercore, but, for instance, the final stage in Blazing Lazers (Gunhed), Gradius series, etc. etc.
I always felt the games were balanced this way to give you a chance if you should lose your power-ups. The difficulty level increases, of course, when your ship can crash into the environment (i.e. the maze level in Cybercore).