Sebastian,
This looks great! I love the results for the example queries.
However, I have a few questions, which I think many people may share. Namely, how is this different from Hoogle? For many of us, Hoogle is the default tool, and has been thoroughly integrated into our workflow. What differentiates Hayoo from Hoogle? Does it offer exactly the same service but with a few different minor choices? (From a very brief glance, I prefer the output I get from Hayoo, but without having used it extensively, I don't know how it really compares.) I think that whatever answer you have to this, it may be good to put on the "About" section of the Hayoo website.
(If the answer is is "it's the same but better in minor ways", that's also perfectly alright. Incremental improvement is important. Not everything has to be groundbreakingly different with strong differentiating points.)
Anyway, don't take any of these questions as criticism -- I'm a huge fan of what I see here and will try to use Hayoo instead of Hoogle to see how it compares in practice.
Best,
Andrew