We are clients of Groupon and have been for a few years. They are a great partner of our marketing group! We have found that the service charge for advertising deals and getting our name out there is so much more cost effective with Groupon than any other format. Yes you might make less profit, BUT everybody is looking for a deal these days, so Groupon is there first stop.
Again, we are very impressed by them and the effort they put in to help you create the best package for your company!