I bought one. It was fine. I didn’t love the operation. It cut the whole top off from the side, rather than from the top in a downwards cut. The sharp edges were on the can rather than on the lid. It would catch the paper labels and sometimes wad them up into the can while you cut. Cans with no air space would leak when opened.

That sounds like a really shitty one, actually. The can openers that operate on the side of the can should uncrimp the top, not actually cut into the can.