I've always had a favourite general-purpose language for personal projects. This has been Haskell for several years now. Yet, I regularly find myself writing things in other languages. I use Ruby at work. I did C++ on a previous job, LISP even before that. I've written side projects in C.

And I'm constantly looking forward to the next opportunity for broadening my horizon, basically looking for a good excuse to learn and apply a new language. But I'm also a person with a distinct thing for languages and their design.

Then again, like somebody else has already stated, learning a new language gets easier every time. I think everybody should learn a few.