I had it done a week ago. My teeth looked good for like 48-72 hours and then the original color came back. I'm not a smoker or drinker. For 72 hours I drank milk and water and no foods with dyes. My top ones look slightly better but the top of the teeth, near the gumline, still look the same. My bottom teeth are once again exactly the same shade I started with.
The original price of the Zoom was $500-something at the office I went to. They knocked it to $300 after I told them that I did not like the process of doing gel and mouth trays. I did 4 rounds of 15 minutes, all of which went perfectly. My teeth looked beautiful afterwards. They said that the teeth gradually get whiter over the next 2 weeks after the treatment. I doubt that's gonna happen though.
I had little or no sensitivity after the first few hours (had some zingers but nothing more.) I read later that Zoom is basically a psychological thing - it does work for a few people, but for most people it's just a temporary thing that makes them ooh and aah over their newly-brightened teeth and the effects aren't permanent. The office gave me some "follow-up gel" which I was told to use in 2-3 months.
Either way, I don't recommend Zoom. I lost 300 bucks. Some people lose 600 or more so I guess I was lucky. I guess I'll try the gel and mouth trays again...I hated them, and also Crest White Strips, but I think that's my only hope. SAVE YOUR MONEY AND DON'T GET ZOOM'd.