I was trying to get going with yesod earlier this evening, and all props to Michael Snoyman, but seeing the Snap Web site makes me far more motivated to try it, and more confidence in what it does.

But, as dons pointed out, crappy docs is not limited to Haskell by any means.

If you want to see your project gain traction it has to be stupid easy for people to jump in and start playing, and solid Web site with serious docs is a big win there (as are project generators and copious examples).