I strapped them on, stepped onto the deck, and... immediately slipped, nearly plunging into the icy cold water below the boat. And, as an added negative bonus (in addition to the near-death experience), I also marked up the deck (don't worry, not permanently):
Then, with the cleats still attached, I stepped off the boat and onto the dock. Much to my surprise, the cleats grabbed hold of the wooden dock, which made my walk down the snow-covered pier feel safe and secure. Apparently, it is our boat's ice-encrusted deck that is the problem (who knew?). I'm sure these little gadgets will come in handy when walking around the city (or parading around in private à la Madonna), but I'll be forgoing them while walking on deck (which I am avoiding at all costs anyway).