Sonic 2 Sky Fortess is awful level design.

Sky Chase is perfectly fine as a palate cleanser and transition between Metropolis and Wing Fortress.
Metropolis drags(it's over fond of those screws that take forever to get you anywhere) and has a nasty habit of putting those crabs and mantises where you can't see them until you jump up somewhere and they attack immediately.
Wing Fortress is mostly fine, but there's that one jump that's a total leap of faith and that's just terrible.
I was never bothered by not having rings on Death Egg though.