Yeah, everybody heard that about HFT. As I said, there people like pointing to that list: http://www.haskell.org/haskellwiki/Haskell_in_industry Many cool names (Facebook, Google, AT&T), but no real products.

> I wonder if it is worth it to learn

Well, you may try anyway. It's pretty interesting experience. Many people claim that after you are "enlightened" you'll hate other languages. Seems that I'm still not enlightened. It's nice to write parsers and similar stuff in it, but I couldn't find an area where it would be clearly better to use Haskell than some alternative I'd normally choose. If you don't need hight performance and your product is, say website, than some Python/Ruby seems more convenient (mostly because of many good libraries and instruments for them). Writing GUI app? GUI bindings for Haskell are pretty awful and unnatural. Real time? Sorry, optimizing Haskell is so unintuitive that I can't consider it. Plus it has big runtime and is lazy. Something hightly concurrent? Not better than Erlang. So, I came up with that it only suites well for writing Haskell compiler and there already is a couple of them.