I have deep set in coffee stains and this has worked well, however not quite as well as a couple other whitening tools. It is good for those with gum issues though as you can avoid the gum lines where as with the strips you cannot.
This is awesome because of the fact that it's so portable, which makes it convenient to freshen your breath wherever you're at if you don't have access to mints or gum. Plus the fact that it helps whiten your teeth ( I use it after brushing in the morning and before bed for this purpose). Love it!
I've never used this product in particular, but have used a whitening pen. I don't find they work well, there's no way to make sure the whitening agent stays on your teeth and doesn't get washed away by your saliva. It shouldn't burn, but if you do get it on your tissue it may cause white spots which will go away in a few hours.