I bought a groupon for Zoom teeth whitening in March. The staff was very nice and knowledgeable. The Zoom whitening itself was not painful (I also took 2 advils before the procedure) but I did have a couple "zingers" towards the end of the treatment. I loved how white my teeth were for about 3 days, then I noticed my natural color coming back slowly (yellowish at the root of the teeth). Although I got a good deal from Groupon, I dont think it's worth it because the actual bright smile lasts for about a couple days.