I installed X2 (using the 'default' configuration). I did get the Dim Pro error warning, so updated that after the fact and it seems to have worked. All the ancilliary installs also went in ok, but I haven't yet looked for Rapture. I know Rapture LE was installed previously so need to look into this.
Having spent a few hours with it, my initial confusion around the UI is receding. Skylight does seem to be delivering what it set out to do, which is a relief. I've yet to plug in a second monitor - I want to place the mixing console on a separate screen and have the tracks on the other one. The ability to switch the metronome off and on while playing is incredibly useful! I find the smart selection tool a bit weird and selecting clips to move/copy is more difficult than previously.
Pro-channels are very nice though I find the compresor a bit harsh, and easily distorts. Not sure on the new eq yet, but maybe I got used to the 8.5 one which was so easy to set up, particularly for the HPF. Console emulation is pretty subtle and I need to play more with that. Not sure what the 'S-type', 'N-type' are - is it supposed to be SSL, Neve emulation?
Is it more stable? Not sure - I had a burst of hang-ups initially and still rely heavily on a lot of 'ctrl-S' combos to have everything secured. For a while it was also hanging every time a loaded an 8.5 project. I quickly applied the patch and it seems to have gone away.
Lots more to investigate but from what I've found so far it makes a good upgrade certainly from 8.5.