I had the whiting done November 2008. My teeth are 9-10 shades lighter, so I am very happy with the results.
The doctor and staff were all very friendly. There was no pain during the procedure at all, but there was some sensitivity afterwards on a couple of my teeth that felt like they had cavities.
My gums were never sore as some of the other people posted. My discomfort disappaited several hours later.