I am using Boots kits -- about 23 quid... to be honest not convinced they have improved anything... my best result so far was with pearl drops and a hard brush and a good scrubbing -- was a bot of a blood bath but teeth looked better... bound to look white against all that blood!!
Have read that most of the ikits you buy are not that good and for real results you need to go to dentist..
A recent review of the products in the mail (readit at work!!) said that one of the better ones is the one that you almost paint on... search on DM websit efor the review...
I'm I trying one that I got from ebay. You are meant to use it every other night until you get teh shade you want. It certianly looks like my teeth have been cleaned brilliantly, but I am sure I haven't used it enough yet (only 3 times) It does contain a high level of bleach - which that article said it needed to if it was to work properly.
I used the Crest whitening gel (o/n for 14 nights) and it was crap.
A few months later I tried the Crest Premium white strips and they were fab. You put the strip on your teeth for 30 mins, twice a day for 7 days. Fabby. My DH's teeth are unrecognisable. However, I would recommend a scale and polish from your dentist beforehand otherwise your teeth look white but you still have bits of tartar between your teeth.
I used the Rapid White Brush on one ( 2 things in one stick) & thought it was rubbish but I remember someone on here saying they thought it worked quite well. SIL went to the dentist & spent about £250 & her teeth look terrific but it only lasts 6mths to a year.