Old thread, but new member...
I've powder coated several engines, including one that's on a 1983 CB1100F that I recently finished for myself. With 1500 miles on the engine so far, there have been zero performance or overheating issues. It's by far the best running, most responsive 1100F I've ever ridden.
This topic usually ends up controversial with naysayers assuming that a thicker finish will be trouble. Since I have a stock 1100F with a painted motor, I intend to collect actual data points from various points on the engines taken at various times during the ride. I'll also check oil temps at the same points and report back.
As far as chips and touch-ups go, the same could be said about a PC'd frame, fork legs, or any other part on the bike that's been PC'd. The finish is a lot more durable than paint and will likely end up with fewer chips than paint will over time. Unless it's a giant chip in a glaringly obvious spot, it can be touched up with a matching paint and the only one who will ever notice it will be the owner.