I do and it is a lot of work for a very small payout. The payout is always stuff too, no gift cards or paypal. When I say a lot of work--they want you to scan everything, many things need more input from you-- so it isn't just scan and go. You have to download each week or you will get nasty postcards in the mail. When I say the payout is poor--it took a year to earn enough to get the Wii gaming accessories--the tennis racket, wheel, golf club and bat???
If you are bored and want something else to do each time you shop and one time per week then go for it, but don't plan on getting anything good with your points for a really long time.