I'm missing something, I suppose. re: has anyone done this/had a dirty power valve?
Sure. It's always a mess. Some bikes with less mess than others, but you aren't going to ever see this assy some kinda clean, shiny, non-gooped looking.
Check the action of the assy by rotating the nut under the LH slotted cover. It should move easily and return freely to the <click> detent (unless you've modified that detent). If you happen to have the pipe off, you should be able to see the subport drums rotate and the main flapper go up and down.
The fact that the assy has smooth action WITHOUT knowing if anything is actually MOVING (pipe off as mentioned) doesn't really tell you much.
Well..tells you something is smooth. Maybe it just don't WORK ;)