Its not worth the time and effort that goes into using OpenOffice on the N900 . The Office Substitutes are great ( and getting better every other week) .
GNumeric - One of the best Spreadsheet Apps that i have come across on any SmartPhone . It can handle some pretty complex xls spreadsheets without even a hiccup. supports most formats.
AbiWord : Great Docment reader and writer .
FreOffice - Has a Spreadsheet, Document Editor and Presentation Viewer/Editor . This has promise , but is very much a work in progress at the moment