So far it's looking good and I have yet to run into any stability issues. I'm playing as the Arceans and had just a few notes/questions.
Note : Severe retina bleeding is happening every time I colonize a planet due to the unique UI features. My race's color is yellow and so when the planet name comes up, highlighted, it is bright yellow with white letters. If you click the name it doesn't fix it, but using the arrows to move the cursor either direction does. As I'd like to keep what's left of my vision, I humbly ask you to change the color in that field when the planet name prompt comes up.
Question : I flipped a terran world and noticed my build queue had three things - 2 were upgrades to terran buildings that I knew how to do better at and one was a Market Center. I had yet to see market center as an available option to build on any of my planets. It was last in the queue, too. That made me curious - was that what the Terrans were working on prior to my flipping them and the upgrades automatically bumped to the front of the queue? I did research a tech that allowed me to build advanced market centers and that market center automatically queued up an upgrade and now blank tiles on my other planets have advanced market centers as a buildable option.
Bug: I alt-tabbed out of my current game to post this and it doesn't look like it is going to recovery from that very gracefully. I can click on GalCiv2 v1.80c Twilight of the Arnor on my taskbar, and the screen goes black. I can hear the music, and my mouse changes to the game mouse, but that's it.