I've used one spreadsheet that has >5000 rows and >256 columns, but the linkages between cells are localized and it doesn't do anything particularly fancy; it just does pretty much the same thing for hundreds of different cases. I've taken it back and forth between OO and Excel hundreds of times, and the only glitch is changes in border/ background colors.
I exchange another smaller spreadsheet occasionally, and encountered one glitch where OO displayed a cell without trouble, and Excel reported a #REF error for that cell and every dependent cell. I think it had something to do with a leading space or something trivial like that. I couldn't debug it in OO until I saw it in Excel.
Mike Halloran
Pembroke Pines, FL, USA