I've finished it. Took me a long wile.
The idea was to do an "edge case" test, and that went well. On a five year old ultrabook with i7 and integrated graphics I've played a 500 star game to a domination victory (it's called "diplomatic", but it's really not). The game didn't crashed and didn't freeze on me. Occasional errors where reported and than "ignored" or worked out. There was one time than I couldn't load/continue, but that bug was worked around and (supposedly) fixed now.
The game scales well, except for the trade pool maintenance, which looks ridiculously and slows almost to death with 3000 trade ships (but you might play the whole game and never open it, I needed only once). Closer to the end game felt a little slow, but acceptable.
As for a gameplay late game turns where too long even for me. Some of that could've been avoided if the "diplomatic" victory where really diplomatic, than everybody vote for 2-3 top candidates and not just for themselves.
I've expressed some wishes earlier in the topic, here are few more thoughts on how to cut micromanagement a little bit:
Colonize Artificial Planets right away - one project instead of two. Allow to terraform Barren directly to Garden or Islands (if the climate allows) like you do with Inferno - one project instead of two. If you allow to build Gardens, Islands or Hives it will be one (expensive) project instead of four - multiply it to at least a hundred (in my case a thousand) to feel the difference.
Add a "buy" button outside of the planet screen. Maybe on the "event" info panel (lower third of the screen). Maybe on a planet picture or on a panel under it (also lower third of the screen). That will significantly reduce hustle in the late game, than money isn't an issue.