I watched someone using one of those loaders at the last high-round-count weekend training I attended, and asked him about it since I hadn't seen it before. He said it was "OK" but flimsy enough that he had broken at least one before. These were for larger double-stack 9mm mags, and it appeared that the same loader might not work on single stacks or different size mags.
I nodded, and went back to chunking away with my UpLULA loader which happily loads mags for every size and shape and caliber 3rd gen S&W I own. I spent a lot less time than most that weekend loading mags.