Whilst I like the concept of this and Numbers (which incidentally appears to be remarkably similar bar infinite scroll), I really couldn't work on a tablet with a spreadsheet. I need a real filesystem and keyboard to be productive. The latter is partially solved with the iPad with a keyboard but why bother.

I tried many times to do it on a Windows Phone with Excel and an iPad with Numbers and it's terribly error prone which is something you don't want to hang yourself with on a spreadsheet of critical data.