I've made around $400-$500 on this site doing the mobile offers they have. Overall I definitely recommend it.
Some offers pay to little for too much work, while others are more reasonable. Th surveys are kind of a waste of time, since you're likely to get disqualified from most of them, which means the time to spend on it is just wasted.
Sometimes the offers don't track for me, and I have to contact support, but they're Sally really good with getting things sorted once you can prove you've completed the offer.