This is one of the modifications which, it turns out, sounds a LOT better on paper and in print than in real life. I only had one encounter with a fish pot (that I know of), and in this case the rope cutter lost the battle and didn't quite do the job it was designed to do.
Story of the Nevis fishing float massacree in 4-part harmony with digital pictures instead of 8x12 glossy photographs with circles and arrows and a paragraph on the back of each one is described and pictured here. And if the for those who don't get the massacree reference, check here.
Update December 21, 2009 - I have to retract my comments about the rope cutter made earlier on this page!
I managed, through stupidity, to entangle the 50 foot rope extension on my dinghy in the prop in the middle of the Sir Francis Drake channel that day and, with a loud <kerchunk> the rope was in the prop and the engine barely coughed before the rope cutter did the job. Unfortunately there was still a lot of rope entangled in the prop, restricting my top speed to about 2-3 knots, but at least I was mobile enough to get a mooring and then go and rent a tank so that I could scuba and remove the mess.
I realize now that in both cases the rope cutter worked perfectly, cutting the rope so that the engine wouldn't go out. My problem was that the remnants of the rope clogged up the propeller - bit in both cases I remained in control of the boat and could, with much diminished speed, still use the engine for propulsion.