Almost all of the people that I've met that read LYAH (including myself) could hardly even write trivial projects in haskell upon finishing it. this is in my book (heh) a failure and why i recommend people to avoid LYAH. If you finish HPFFP you have everything you need to be productive and contribute to a production code base.

If you learned Haskell using LYAH and you could write non-trivial software in Haskell right after finishing it - I'm very happy for you. But know that you are in the minority from what i got to witness.