Pros:
Small, full featured. Easy to use, so far.
Cons:
I'd like to start off by saying that Gnumeric 1.10.16 is the best spreadsheet since Excel 2003 for reading Lotus wk1 files. However, it seems to ignore the column widths of the Lotus files, and more importantly, does not maintain the status of protected cells. That second problem being the most significant.