Most people say that because power equipment can wreck a blade fast if done incorrectly. Stones, if done incorrectly, take a lot longer to wreck a blade.
I bought a set of paper wheels and, to be honest, I'm not any good at it. They aren't as easy as some videos make it look. My first thought was that they were defective... but I'm cognizant of the fact that most newbies are probably apt to say the same thing regardless of the product. Heck, when I first learned to ice skate I felt that the skates were improperly sharpened (but come to find out I just didn't know how to skate). Paper wheels are probably the same.
I'm practicing with cheap knives (think gas station cheap) and they won't get sharp. This could just be the cheap steel, but I'm hesitant to try it out on a "good" knife. I'll probably have to try a 8CR13MOV blade which, even though it is one of my favorites, is still inexpensive to replace.
One nice thing, though, is that they can remove a lot of metal if you want to. I intentionally took the serrations off a cheap blade and it took hardly any time at all.
-StaTiK-