Reviews have been coming in since the launch, and overall they've been very good. Here's a roundup of current reviews and we'll continue to add more as they come in.
PCGamesN: (9/10) "running a vast galactic empire is absolutely worth the effort"
http://www.pcgamesn.com/galactic-civilizations-iii/galactic-civilizations-3-review
Rock, Paper, Shotgun: "a fantastic update to one of the best 4X games in existence"
http://www.rockpapershotgun.com/2015/05/14/wot-i-think-galactic-civilizations-iii/
GameWatcher: (9/10) "This is the new gold standard in 4X space strategy"
http://www.gamewatcher.com/reviews/galactic-civilizations-iii-review/12232
IGN: (8.6/10) "Galactic Civilizations enjoys such a wealth of victory conditions and customization options that the experience feels new with every playthrough."
http://www.ign.com/articles/2015/05/14/galactic-civilizations-iii-review
Softpedia: (9/10} "a great game, containing a mix of familiar mechanics and new ideas that can keep both fans and newcomers occupied for a frighteningly long period of time."
http://www.softpedia.com/reviews/games/pc/Galactic-Civilizations-III-Review-481177.shtml
The Escapist: (4/5) "Galactic Civilizations III gives players thousands of hours of game. Before multiplayer."
http://www.escapistmagazine.com/articles/view/video-games/editorials/reviews/13921-Galactic-Civilizations-III-Review-Gal-Civ-3-Takes-Turn-Based-to-
eXplorminate: (Recommended) "With GalCiv III, I think Civ might have finally met its match in the cold depths of space."
http://explorminate4x.com/2015/05/14/galactic-civilizations-3-review/
Game Informer: (8.75/10) "clever planning and diplomacy are as powerful as beam weapons and starship shields"
http://www.gameinformer.com/games/galactic_civilizations_iii/b/pc/archive/2015/05/15/a-capital-starship-in-the-4x-galaxy.aspx
VentureBeat: "Galactic Civilizations III reminds 4x strategy fans what it truly means to go beyond Earth"
http://venturebeat.com/2015/05/13/galactic-civilizations-iii-reminds-4x-strategy-fans-what-it-truly-means-to-go-beyond-earth/
Hooked Gamers: (9.0/10) "Galactic Civilizations 3 is a phenomenal game"
http://www.hookedgamers.com/pc/galactic_civilizations_iii/review/article-1478.htmlv
PC Gamer: (87/100) "GalCiv 3 is easily the best recent 4X of this scale."
http://www.pcgamer.com/galactic-civilizations-3-review/
Eurogamer: "the game is well deserving of the GalCiv name and offers enough in the way of traditional features and modern scalability to secure the series' place at the very top of the 4X tech tree"
http://www.eurogamer.net/articles/2015-05-25-galactic-civilizations-3-review
Eurogamer Germany: "One of the best 4X strategy games of recent years."
http://www.eurogamer.de/articles/2015-05-19-galactic-civilizations-3-test