I found a Groupon for $99 so I figured I would try it out. The technician took some pictures with a little camera and put a plastic thing in my mouth to keep my lips away from my teeth. Then she put coated my teeth with a gel and used some kind of light to dry it on each tooth. Once it was on all of the teeth, she set up the Zoom light in front of my mouth for 45 minutes. I didn't feel anything in my mouth the entire time. When the machine turned off, she removed everything in my mouth and I looked in the mirror. It was much whiter. I can still see some parts that are whiter than others, which they told me would happen. It's really not noticeable unless I'm looking in a closeup mirror.
I was in the office for about 1 hour and 10 minutes total. Once I was driving home, I felt the first sharp pain in a lower tooth for about 2 seconds. I continued to feel that about 3-4 more times during the next hour but after that, I didn't have any other sensitivity or pain.
I have followed the instructions and only ate colorless or white food to prevent staining for the first 24 hours. I think it was a very good experience!