They are legit, but as I've been a member for probably 5 months now, I have yet to actually fill out a survey. I fill out the pre-survey and get told that my responses don't make me eligible for the real survey and they give 3 credit points.
It's not worth the time for me, perhaps your lifestyle is different so you'll qualify for more (i.e I don't go to the movies, watch TV, eat out and many of the surveys are about that).