I was mainly referring to Numbers on iPad, which I use much rather than Numbers on OS X. I do however occasionally use Numbers on iPhone, when I don’t have an iPad or notebook with me. It works fine for looking up information, make small edits, or do some quick calculations (although I mostly use Soulver or WolframAlpha for that).
Then again, I carry my air on me everywhere I go, so I'll never, ever be editing spreadsheets on my phone. Seems like an odd usecase to me, though.