I do them from time to time. But you have to do so many before you accumulate real money that most of the time, they're not worth doing. I mean... 20 min of filling out all these annoying questions for a dollar? I would do it for 5 bucks, but not one dollar. And be careful- some say they'll give out money, but they give out gift certificates for cheezy poofs, and not worth all that much either. So if you do them, just be careful and look at what they say the reward is before you commit yourself to 20- 30 min of mindless questions so you can receive 30 cents.
Oh- and if they pay you cash, they pay you through paypal... so make sure you have a paypal account set up.