I was kind of disappointed that the purifiers that spawned next to me in my last game never declared war at all, despite being advanced starters. Something bizarre was happening when they tried to expand into one of the systems adjacent to me, where their construction ship would fly into the system, then halfway to the star, and suddenly teleport back to the system it came from. Must have happened hundreds of times before something happened and it finally finished the construction, but by that point I was too powerful for them to mess with me.
Anyway, after beating that game I went back to pick up the game I abandoned where I thought I was going to lose to the Unbidden. My main problem in that game was a weak economy, partially because I was in the middle of the War in Heaven and my allies kept conquering systems that flipped to me, and since they were badly built up the planets were a net drain on my economy. Couldn't release them as vassals either since I was in a war. So... I just disabled all of the buildings and forgot about them. I'll let them go as soon as the war ends. Until then, I've redesigned my ships to use pure kinetic weapons and have focused all research on improving shields and kinetic weapons. Battles with the Unbidden have been going much better, and I think I can turn this around now.
On the subject of the 2.3 patch, I'm really looking forward to habitats and ring worlds again. Habitats in particular are going to be so much better now, since they can build most of the buildings they couldn't previously, and can get mining, energy and science districts now if built over celestial bodies with deposits. The districts also provide housing now, so habitats can have larger populations. Ring worlds look like they're going to be more like ecumenopoleis now, so that's good too, although I'm sitting here and wondering why you'd ever build a habitation segment with 70 housing when you'd never employ all of the workers. I'd expect that even small decreases in housing utilization the other segments would give enough spare housing to give enough pops to work any buildings you build.