> Half tempted to just clean up the
> piston and rings and put them back and > compression test the thing.
I've done that in at least 2 motors. If the rings aren't horrible and have some "spring" left to them, get the rings and piston cleaned up and do a little bit of sanding in the cylinder to clean up some rust there, reassemble, and give it a go.
A motorcycle mechanic felt that the action of the rings might clean up the cylinder as well. I'm not sure I would go riding the bike, but at least you can give things a listen and see if it sounds like something horrific is wrong with the motor.
In all reality, though, if the motor took a month to free up, I would worry about bearings and seals. I would plan on a rebuild if I were you.