*Updated July 2, 2014*
[NOTE; This isn't so much a review of the game and more of an... 'opinion piece' for lack of a better word. The game is far too early in development to begin making a rational and justified review. Also, as a very large fan of the previous 4 games (Galactic Civilizations 1 & 2 on the OS/2 in the 90's, and Galactic Civilizations 1 & 2 in the 2000's) my opinion is likely biased to some extent.]
If you were not a fan of the previous game(s), don't squander your money on something you will almost certainly not enjoy. 4X games and Galactic Civilizations are an aquired taste, and if you haven't played earlier iterations you'll be wasting your money buying the game at the moment. Buy "Galactic Civilizations II: Ultimate Edition" here on Steam for a few dollars to see if the series interests you.
At the moment, the game is in alpha testing, and as such is woefully inadequate as a game in and of itself. Almost every mechanic, from diplomacy to planetary invasions, are either not in the game or are present in only the most basic way. If you buy this, you do so knowing that it will not be 'fun' for several months at the very least. Do so only if you truly wish to aid stardock with feedback and testing. (EDIT 2; the game has recently been updated to include the ship editor. It kicks ♥♥♥) (EDIT 3; Several features, including shipyards, resources, game options and larger maps have been released! The AI has also been updated significantly)
That being said, the alpha is totally playable despite its limited set of features and options, and while it obviously has many bugs, it is nevertheless stable for prolonged periods. It's not overly fun, but then again it's not supposed to be. (EDIT 3; I can say now with some confidence that a regular person will have a good time playing the game)
So yeah; buy this (July 2 2014, Alpha build 3 as of writing) if you want to help out the devs or if you're a long-time fan looking for a better long-term deal, not if you're looking for an overly enjoyable experience. If you're someone with the latter inclination, wait for release day or Beta access in the summer (August-september).
EDIT; it's worth repeating here that you get all the DLC that will ever be made for the game if you pay the $100 asking price. They currently have 4 major expansions, alongside several smaller DLC's planned for undetermined release dates up until the year 2020. If the quality of previous Stardock DLC holds up (Think Twilight of the Arnor, Legendary Heroes etc...) then this will ultimately be a very good long-term investment.
EDIT 2; Stardock has recently updated the game to include the ship designer. To put it mildly, even in its current, rough and unfinished state, it is better than any other ship editor I've played outside of dedicated modeling programs like Maya. The game has taken a big step towards having my review changed to a general-user "Recommended".
EDIT 3; Another major update has been released by Stardock. To make a long story shot, the game has been massively improved. The AI has been upgraded heavily, so it is now capable of actually playing! Not to mention the inclusion of a novel new ship building mechanic (shipyards), on-map galactic resources, a revamped planet generation system, a massively-expanded tech tree, basic effects, an overhaul of the planet and production screens, race heterogenity and several other things. I suspect I will be forced to change my review to a "recommended" next update, as the game is getting progressively much better!