That is great to hear! I'd love to read the details if you happen to have a link to more information. I've tried Googling for it a few times over the years but never found anything.
I haven't done any work to implement refinements myself, but I do know that basically it came down to something that you could write an inline cache against, guarded against the class version, so a simple word guard that you were doing anyway when you called any method.
