Which is one of the finest software ever written in the history of software.
Edit: glad you were not being sarcastic :-) thanks for clarifying
From what I've seen, the the spreadsheets themselves are great, but the lack of good version control, revision tracking, and regression testing makes for poor operational processes.
People e-mail one another Excel workbooks, there's 5 different versions in flight at once, and impossible to find when an error or mistake got introduced or who was responsible.
http://www.proudlyserving.com/archives/2005/08/dos_aint_done...
Actually what I remember is that Lotus killed itself by not having a windows version on time.
They actually believed when Microsoft said OS/2 was the future. That probably killed some of their competitors.