I doubt anyone has valid stastics to answer this, but I'll throw in yet another anecdote. For about five years I used Python for all my personal projects, then for a couple years I switched to Ruby because I was using it at work. Last year I switched to Haskell for everything from simple command-line scripts[1] to larger programs[2] to silly recreational programming[3].

[1]: http://github.com/mbrubeck/outline-grep

[2]: http://limpet.net/mbrubeck/2009/10/30/compleat.html

[3]: http://github.com/mbrubeck/mynock