Hi! The download page says that the questionnaire module "Requires a somewhat unorthodox setup procedure." This sentence made me turn away from this wonderful add-on until I now finally dared to have a closer look at it.
I don't really know how to define "orthodox" but installation was easy: Upload the content of the zip into /mod, got to www.mymoodlesite/admin - and that's it. I really think that this sentence should be deleted so that other users dare to install it much earlier than I did. You did a wonderful job - thank you very much!