I like GalCiv3, especially with the expansions & DLC included. (I concur the base game at release was something of a turd.)
In its final form, I put it solidly in the "good" category. It's not amazing, or exciting, and it's not going to push the genre in a bold new direction. But it *is* technically sound, runs well, is highly polished, has competent AI, and it offers enough new wrinkles to keep things interesting.
I like the ideology system, and its associated perks. I like how all habitable planets have some type of "specials" that help make them unique. I like the Citizens mechanic, and how they boost your empire. I like how Starbases function, *and* that they finally figured out a reasonable way to eliminate the old Starbase "spam". I like that the races all "feel" different, both when playing as them, and interacting with them. I like how mining/acquiring resources work; I also like asteroid mines. I like the high degree of game setup & customization options.
However, I am going to partially disagree with you on the ship designer being a standout feature, and that's related to one my chief critiques of this game: the complete lack of tactical combat. As long as Stardock continues their steadfast refusal to implement any sort of actual battle system in their GalCiv games, it renders their ridiculously in-depth ship design feature virtually pointless. You might as well go with a simpler, more streamlined ship designer like what Stellaris has.
Other things I'm less wild about: Colony management is...sort of fun?, yet also a bit too byzantine for my tastes. Diplomacy remains simplistic (although to its credit, this means the AI is better able to handle it). The fact that you have to *research* new types of treaties (like Alliances) drives me nuts, especially from an immersion standpoint.
Perhaps my single biggest gripe about the game, however (other than perhaps the combat, or lack thereof), is that it feels somewhat...bland. And it's not just GC3; the entire series has suffered from this problem. Brad Wardell created an entire backstory for his universe, complete with lore, notable characters, and dramatic events...and then proceeded to lock it all behind separate, story-based campaigns, rather than folding it into the sandbox campaign that just about everyone prefers to play in.
(Fortunately, it appears that, going by his posts in the Stardock & GalCiv forums from the past several months, Brad has finally taken this lesson to heart: Galactic Civilizations 4 won't have a separate campaign. Instead, lore-based events and event-chains will show up during the course of a normal game, just like in Stellaris and Distant Worlds. This should bring some much needed flavor -- some life -- to the series, that heretofore, had sorely been lacking.)
Seriously, though, I only criticize because I care. I genuinely do enjoy GalCiv3; it's earned a permanent spot on my hard drive, at least until GC4 is released.
It's just maddening when the game does so many things right, but then misses the mark in a few crucial areas. Gah!