Hi there, extremely long time since I've last posted, about 8 years I think, but I've been lurking (sounds a bit sinister) around the forums a fair bit over the years, and have been a huge fan of the franchise since I picked up a copy of Gal Civ 1 as a really random impulse purchase in a little independent game shop (long since closed) about a decade ago now!
I totally missed the announcement of GC3 until very recently. Thankfully I came back and saw the announcement on the Forums before it popped up on the front page of Steam, or I may have died of a joy related heart attack!
Anyway, I've spent a few hours with the Alpha and just wanted to share the bugs I'd come across/observations I've made.
Game looks fantastic so far by the way. I'm really looking forward to seeing it develop, and playing the final release. I particularly like the opening video, music, and ship models. Awesome stuff. No regrets about the purchase whatsoever – any and all criticism below is designed to be purely constructive! 
Bugs & issues (+ one typo):
Spelling error - "Games of strength" in malevolence tree reads - helps "bread" stonger citizens, rather than helps "breed".
I had 4 military ships, and they all seemed to exploring the same area of the galaxy together, on at least one occasion this area was already explored. I think this was because there was nothing left in their range to explore. I think it might make sense for the game to notify there is nothing left to explore within range, and cease movement instead waiting for new orders.
I like the fact that you can use the keyboard keys to move around, and when you are zoomed out the sensitivity is great. When your zoomed in however, key presses lead to getting jolted across the galaxy at breakneck speeds! I think sensitivity of key movement should be adjusted with the level of zoom.
It would also be great if WASD were default keyed for movement - if these keys are not earmarked for anything else.
I get a bit of an occasional audio stutter. I use on board audio on a PQ5-Pro motherboard - if that helps!
The tooltips and clarity of explanations still need a bit of work - especially on the tech tree and on the planetary UI. There are numerous explanations around what certain techs do re altering "caps" that I'm still not certain about - although I do have a tendency to play with a beer, so maybe that's not helping 
Notifications don't seem to pop up when ships have been completed - sure this has already been mentioned.
Notifications don't pop up when constructor arrives at a starbase and is used up - so you get no prompt to choose a module.
I had a small planet, filled all the construction tiles, but then still got prompts from the end turn button to build on an "idle planet" after all construction was complete - I need to check this to see if it was because the game wanted me to upgrade a building - either way, it seemed like this could be handled/explained better - or it's a bug.
When you are rushing stuctures, I think the cost needs to be more apparent than a tooltip over the buy button. I didn't use the credit options for purchasing/rushing much - but do miss their absence a little from a "flavour" perspective.
Gameplay Feedback
I'm a bit dubious about the removal of happiness and tax. It all seems to be a bit over simplified like this. I really like the level of complexity in GC2 (I have a game on the go at the moment), and I love the way the game forces me to shift my focus between different elements of the economic and political playing field to get my empire running smoothly. I think maintaining happiness and a balanced budget was an important part of this.
The bits I seem to be getting from anomalies seem game breakingly high powered.
Ships are looking pretty awesome, but planets and stars don't look as good, and (in my opinion) probably need some more attention if they are not going to look out of place, or ugly by comparison.
My initial feeling was that I liked the way techs are broken down into their relative fields in the text view, but I miss the option of looking at the visual representation of the tech tree. I like certain elements of the "three starred" techs too - with multiple research options - but didn't realise what this was/how it worked at first.
I really like the fact that now the galaxy has terrain - the dust clouds pop out a bit visually though. I had a thought on this, and wondered if it might be good to have "dust clouds", and then "thin dust clouds" wisping around the outside edge of cloud clusters. These could provide 1/2 or 1/4 of the affect of the full cloud. This would help to blend them in visually, and could also add a little extra strategic depth to them
Narrative issues - My favourite part of the Gal Civ is the sandbox style open ended games - As it stands, in these games, there's something odd about starting out from the terran homeworld and growing your civilisation into the galaxy, with other races thanking you for hyperdrive etc - then finding loads of remnants from a war that your people have previously fought with those races before. I.E - old terran ships and whatnot.
I like finding the stuff though, it adds character to the universe, it just fit together better in previous Gal Civ's because the artifacts you were finding were from the ancient pre-cursor races. I suppose you could frame it so that races were recovering from a kind of dark age? Or will these artifacts be removed from the post release Gal Civ 3 sandbox, and replaced with something that fits the story better? Perhaps the campaign and Sandbox could have different artifacts for discovery?
When you colonise planets, sometimes your colony capital plonks itself down on a high value hexagon - this can be frustrating. Could players be allowed to either choose the location of that structure to try and avoid these valuable locations, or could it be placed on a separate blank tile? Perhaps alternatively players could be allowed to place the capital, and could receive relative bonuses for setting down on squares that would usually provide percentage boosts. E.G + 2 lvl to finance could provide a standard X bc credits per turn (2 perhaps, or 4?)
I played GC2 recently, so it feels a bit counter intuitive at the moment that I can't double click on a ship to give it particular orders, or upgrade it. This could be just a teething issue though, and may make more sense in the long run - or it's just a UI option that you haven't built in yet.
I'm not a huge fan of the single build queue but LOVE the sound of where your going with that in “SY100” - so no complaints there! 
Thoughts on future development
I hope the game breaks away from the rock paper scissors element of lasers, bullets or missiles a bit. It's not that I want those elements gone, but I am more interested in the ideas of ships having different ranges, speeds, accuracy, evasion etc. Maybe even stealth abilities, EMP, boarding, teleporters, etc etc... (I can dream)!
I would like to see some improvements to the space battle parts of the game. I'm eager to see what you have planned and don't have any big ideas around the functionality, but would really like to see 2 things from a cosmetic stand point:
1) large ships behave like large ships cinematically, moving in a steady fashion, rather than nipping around. I always thought it broke the fourth wall a bit in GC2, that you'd make this enormous powerful goliath with all of your resources, and then it would just whip around the combat screen like a small fighter
2) Ships firing their weapons from logical - perhaps user defined - point on the ship. In gal civ 2, weapons were frequently fired from thin air, and it broke the illusion a bit.
2...a) Weapons should hit enemy ships visibly - when they hit - and miss visibly when they don't. Some decent explosions, visible damage, and nice chaff, armour, and shield effects would also be good!
Anyway, that’s it from me for now – apologies for the essay! Hope some of that is helpful, or interesting, or something else of value... 