Spent $400 for Zoom Whitening in 2010. I had very minimal sensitivity. My teeth did get a lot whiter and looked great - for about a week. 1-2 weeks later they looked pretty close to what they did prior to whitening. I was given an aftercare kit which admittedly I didn't use consistently. The bottom line is if you do in office whitening you should plan on being very consistent with at home care or results won't last at all.