Played a few games of GCIII Alpha and thought I would share my thoughts like everyone else has. 

First, I enjoy the new UI's look and feel.  Love the color coded lines when you send ships to a destination, and love the way they turn and fly on the map, very nice touch.  I know that a tech tree is coming, and it will be welcomed... the way you currently select items in the Alpha would be great if you knew the tech tree, but now its a bit of hunting and guessing to find a tech that would open a desired "goal tech" two or three levels away.  Like the idea of unlocking various skills based on alignment decisions.  I like the planet and ship view on the right side of the UI, but would still like to see a chart/graph/list system as a tab option.  I also hope that the "planet manager" system (for example changing all planets that are currently making constructors to have them make star fury fighters).  These tools make managing a large group of planets easier. 

I'm not too crazy about not having both starport construction options and planet building instructions simultaneously.  It's something I could get used to, but I liked that capability in GC2.  I also hope that you would add the GC2 ability to automatically upgrade planet improvements as new ones are available. ... or at least the option to allow it for those that do not want to micro-manage that process.  I love starbase construction and it appears that job-specific starbases are a thing of the past... noticed you are restricted from putting starbases too close together, that seems to support the theory that you can have a single military, cultural, and economic producing starbase.. I'm ok with that so long as each of those functions can be fully upgraded and not limited by module capacity.  I also like to see how adding modules changes the look of my starbase... didn't really see that in the alpha.

 The alpha runs very smooth for such an early build, and I never felt like it was going to crash at any minute like I feel in late game on a huge/gigantic map in GC2.  I hope that this game will allow me to play epic games without the late-game crashing of GC2.. I know my computer can handle it, and I hope that GC3 is 64 bit.

I have run into many of the glitches folks have already posted on the here: flashing text between turns, battles not engaging, typos, odd planet tile placement, so no need to rehash them unless you want me too.  Ship building is such a great part of the game its sorely missed in the alpha build... but the ship builder screen leaves me slightly underwhelmed as to the detail of the ship graphics... the ships seem to have this washed out or over exposed quality to them... appears to just need some texture improvements.

So many neat things in GC2 that I hope are carried over with greater depth and detail that are not in the Alpha build (as expected) that include: robust diplomacy, trade, asteroid mining, indications of cultural pressures on mines and planets (pending revolt icon), race customization, politics, united planets, etc. Just love all of that complexity and depth and hope that it carries forward as we see the beta and final versions.  I will post more to this thread as I find/discover any issues.  Overall, the UI and the polish of this game in the Alpha stage has me very excited and hopeful about the finished product.