Actually the worst/best thing about Numbers is the way keyboarding on screen is handled (worst in that it's still the worst, best in that they've clearly thought about it and worked hard to make it less bad than it might have been).
I think a spreadsheet app that really figures out a solid way of working around the lack of a hardware keyboard might do well (e.g. allowing you to format cells as sliders or spinners or whatever so you don't need to key in values).
You can hook up a keyboard to your iPad, if you like. Not sure if that would solve your problem. Keyboard support is on our planned list of features. Most iPad users are fine with the touch screen keyboard, so we haven't prioritized physical keyboard support yet.
I do like where you're going... just had to edit a Google doc spreadsheet on my phone (painful). As a long-time Excel user,I just can't imagine giving up keyboard shortcuts, etc.
