Overall, I've been fairly satisfied with e-rewards, although as Kathy states some surveys take several days for the rewards to post. Once or twice they were significantly late (over 10 days) and I had to get on their case a bit.
It takes a fair amount of time and effort to earn significant rewards, but I'm able to use e-rewards to keep the Wall Street Journal coming (6-month increments for $50 in e-rewards), and pick up 3,000 Hilton HHonors points every 90 days.