Well, I'm using it for a project at home. But that's because I am learning Tk and DBI at the same time, and performance is not an issue here, so I didn't want to deal with learning MySQL as well.
I guess a lot of it depends on what you're using it for. At work we have SQL 7, Oracle, and Sybase databases. Not to mention lots of Excel spreadsheets doing stuff that should be put into databases!