After a few months with it now, I am finding a few niggly little things in PRO that I never noticed in Xtreme. None of them are show-stoppers but they certainly go against the "Pro" name of the application.
First are the disappearing scroll bars. I haven't used Full-Screen Mode for a couple of months but my scroll bars still come and go, depending on my zoom level. It gets really frustrating sometimes.
Then there is the overall speed. Moving things around seems a lot slower than it used to be, once you get a few objects and some transparency going. I tried to recreate the appropriate optimisations but as I had to do a clean install to get it running at all, I can't be sure I did it properly. TBH though, it might just be an impression but it is a strong one.
I also find the docked palettes sometimes get a mind of their own, reorganising themselves. Again, it's not a big deal, and it happened in Xtreme too, but all these things add up to slight disappointment for me. If I didn't have printed manuals and a new box, I would probably feel that I had completely wasted my money on this upgrade.