I had my teeth whitened twice. The first time was about 6 years ago. I did it again about October of 2009.
I really don't understand how people describe it as "excruciating" or painful. It's more annoying then anything else. The process of sitting there with a light in your mouth for an hour is pretty nerve wracking, but it's only an hour. Right afer and i guess for roughly a day or two, you get this sort of "zing" in your teeth. It's hard to explain. I guess I can only compare it to biting into something cold with your front teeth. I say "zing" because it comes from nowhere & goes away quick.
I went to the office in soho both times. I did notice a HUGE difference in my teeth. Perhaps because of my skin color it made the color seem even briter. At any rate, the office is nice but the receptionists were very rude. They barely made eye contact with me & decided I wasn't cute enough to talk to. I say this because they were chatting it up with some younger girls from england & barely said two words to me. Hey... Whatever.
I do recommend the treatment. Just don't go thinking your in your friendly neighborhood dentists office. NO WAY!