Don't get fooled my friend; at this stage, the ported version of gnumeric is unable to open/handle most of .xls files.
Also, I've found a major bug, which is when you try to open a .xls file, Maemo ask what program you want to use to open it, and when you go to select the program, guess what: gnumeric isn't listed...nice joke.
So because of that, the alternative is open gnumeric, go to file-open and select the file stored and guess what: gnumeric closes..or if it's able to open the file, it will show you wrong values, changing date format, showing ---- on cells (?) and other stranges things.
So my conclusion is, at this time, forget to use your N800/N810 for any serious MSOffice handling.
Productivity with the N8XX? Maybe for some users, not for all.