I used Aquafresh White Trays when I had a big event to go to - and I had several people mention how white my teeth were! Unfortunately the effects are only temporary - especially if you drink a lot of coffee and dark sodas (like me). So yes, they do actually work!
My teeth are SUPER sensitive (I can't bite into ice cream with my front teeth), and I didn't notice any change in the sensitivity. If all else fails..just ask your dentist if you have serious concerns.
Good luck!
Bronwyn xx