Maybe. Fly I'll give you as being major. Fireball not so much, in that though it looks big and impressive and it's hella fun to cast there's often better ways for a Wizard to mess up the opponents. And the 100 h.p. character was 90 h.p. yesterday; and 2 attacks a turn (at least in my game) is only jumping up from 3/2 attacks, so those are more incremental
Fireball is The game's first real room clearer.
100 hip points pulls you out of Power Word Kill range.
And two attacks a turn doubles your damage or major targets in combat.
Each edition had their own types of "Switch on" abilities and they tended to coalesce around certain level ranges.