At least, it is the only one that I could easily FIND without alcohol - I do live in a smaller town so our range of products may be limited. For many people, it is critical that a mouthwash not contain alcohol, as that substance is absorbed on the tongue, thus gets into the system even without swallowing.
I can smell/taste the hydrogen peroxide after use. Apparently the gasses travel from the mouth to the nasal cavity, which if I recall my anatomy training correctly, is logical. I am willing to put up with that if the bleaching action works because I am unhappy with the appearance of my teeth and unwilling to give up various foods that stain them. I am also thinking that I will use this mouthwash for a period of time, then return to my regular one. And plan to keep swapping off.
I have not (yet) noticed any of the adverse reactions reported by other users. However, I do feel the same sensations caused by the Crest Pro-Health "multi-protection" rinse I had been using prior, which is to say that a tingling is produced that some might even call pain. Because I've been using a mouthwash right along, I've come to expect this sensation and associate it with my mouth getting cleaner, bacteria being killed.
The bottom line is that my teeth are becoming whiter over several weeks. My marker is one capped incisor that unfortunately matched my teeth 'way back when and now is far too white, creating a telltale contrast. I think my aging teeth are simply becoming translucent and I'm not sure anything can correct that. But with this whitening rinse, they definitely are better.
UPDATE, Nov. 4, 2011: I want to report that I have been using this product daily for 5 months now without any of the gum-pain, bleeding or tooth sensitivity problems reported by other users. Apparently these are problems for some but not for others. I want to be clear that I don't doubt the reports of others; I am simply stating that with long-term use, I have not experienced these negative results.