I just received my gel and kit today. I used it for 30 minutes this afternoon and my teeth are whiter already. My teeth were not real yellow to begin with, but definatly needed whitening. I cannot wait to use the product for the rest of the week to see what results I get. I did experience some sensitivity on the gums, but nothing that wasn't tolerable. In a few areas my gums did turn white from irritation, but quickly recovered after taking the mouth piece out. It really is very hard to avoid getting the gel on the gums, but whiter teeth are worth it to me. The product arrived quickly, with all the pieces in place. I recommend using this product for sure!!!