If you want a premium case, Corsair has abandoned a lot of what made them great (build quality) to gain additional features. Phanteks Enthoo Primo is the current king of non-specialized cases (Case Labs, Little Devil, premium Lian Li) right now. Heck, even a lot of the NZXT stuff is nicer.
I think they do a lot of great stuff, I especially like the 350D and Air 540. But the 750D and 900D are really large and cheap.
My main desire to move up from the Air 540 is that I need more 3.5" disk space, which leaves me hunting for full towers, also the horizontal desk space turned out to me more of a premium than i thought.
Currently digging through Caselabs options, they seem to have a big following on overclock 3d