I think a lot of people look at these white strips and think that they are going to perform whitening miracles on their teeth based on the advertisements that the company put out. While they aren't the best whiteners out there, they do bring your teeth a few shades up the ladder as long as you avoid just about everything that could yellow your teeth. It's not a bad product by any means, but I certainly expected better.
As far as whitening goes, I saw results a few weeks after I started using these strips. I would expect that most people won't even notice the difference, but I took a picture every nigh of my bottom teeth and noticed a slight whitening difference a few weeks in. It is still pretty great to me that they do actually reverse aging on teeth, but I don't necessarily think they are worth the money.
I can recommend this Crest white strips because they do work, but I have to warn others not to expect a whitening miracle of any kind. I would suggest to check out other whitening products, as well, because chances are there are cheaper options out there that will give you a comparable effect.