I've just made a list of things I love in Fusion, and there's a few that keep it from being a 'classic' game in my heart. Not game-breaking, just really annoying:

1. The speed. Waaaaay too fast. (this coming from somebody who can't really handle Phantom)
2. Kerb-hopping off the track (comes from number 1)
3. Trackless sections with bits of rock and junk getting in the way.
4. Temtesh Bay's trackles- OH GOD MY EYES!
5. The pit lane never seems to fully recharge my shield;
6. Ships with different shield strengths.
7. G-Tech. Just...no
8. The Flamethrower. It'd be cool if it covered the track in a searing inferno...
9. That one flip-pad door-section on Katmoda 12 that ALWAYS destroys my ship
10. The font. Small TV - can't read it. Large TV - can't read it.