I'm the exact opposite of Capt. I use my Polish Capper all the time. I have big sausage fingers. So capping by hand is a royal pain for me. Fumbling around with the cap is frustrating. I also find that loading the capper is simple. Dump the caps in, shake it until they're all right side up, and away you go.
I even made a little holster for it, so I can carry it on my belt.
I tried the other cappers too. But didn't have much success. The straight line cappers are useless to me. If the little spring steel fingers get out of whack at all, the caps are dumping out all over the place. And when capping the pistol, more than one seems to always come out.