most of their incentives are entries for drawings (2 - 1 for 100 and 1 for 1000 i believe it was) but they say for a few things they pay directly, for some sort of lab thingie or something.
just checked their website. They will eneter you into monthly drawings. must of changed the incentives
They pay in amazon.com gift certificates and they don't send you invitations unless you're qualified to take the surveys. Once they send it to you, all you have to do is finish it in decent time because they'll only accept so many. Usually pay within a couple weeks after completion.