I've not really dove into it because I'm not doing much on a spreadsheet on a phone, nor am I sure a tablet would have the horses to handle many of the spreadsheets I work with. And still no MS Access, but that's a minor nit.
But I always thought that while you can create and edit documents you are dealing with stripped down/limited applications or reduced functionality. Even WINE on Linux I think is still a bit wonky or limited so it's inconceivable to me that an Android app would be better. I may be wrong.