I've used SeaFoam as an intake decarbonizer for the upper air/fuel system. It seemed to do a queationable job; not much proof as to whether it worked or not. I don't think it did any harm, but it didn't seem to produce any amazing results. I've also used Techron for an intake cleaner, too. Again, I cannot say for sure how it performed, as it's hard to quantify the results.
ARX, on the other hand, has performed FANTASTIC results with the same car, regarding compression restoration. This success story is well documented here in this section (search my user name and "Taurus Vulcan". I'm in the rinse phase right now, and I have nothing but praise for ARX. Here, I can show definitive proof, with tangible evidence.
The reason people praise ARX is because they've used it and seen the results. The only reason I suspect people not being impressed with ARX is because they're skeptical (probably because they've not used it in a situation where they can doccument the results). I cannot fathom anyone who would use ARX, properly doccumenting the before/after relationships, and not be impressed.
I too was skeptical until I tried ARX. I did a decent job controlling the experiment, as much as any other testimonial I've read. I am now a convert.