I've taken a few from
http://www.webperspectives.ca, mostly just to kill time at work (ironically, working for another market research company. But I don't tell them that on the survey, otherwise they won't continue the survey).
Most of the time, it's just something like "you're entered in a monthly draw for $1000!". I did take a survey from them that offered $5 paid over Paypal for completing. It arrived a few weeks later.
Simarly, the company I work for mostly offers an entry into a monthly draw for completed surveys.
But the site you linked to? Looks unprofessional and reeks of fishyness and scamminess, if those are actual words.