Being an old timer who played these things as board games back in the 70's, I don't get too worked up over the UI stuff. At the risk of sounding like Grandpa talking about how he walked 10 miles through the snow to school every day, I had loads of fun playing Stellar Conquest and that meant keeping MOO1-style records on every colony in your empire with pencil/paper/calculator
What I do care about is features & "game mechanics" (i.e. the "rules", including customization opportunities). That's what makes a great game to me.
OK, I played the tutorial and am about 1/2 way through a "full" 100 turn game with my own custom-designed race (using the Terran shipset). Here's what I think so far...
I wish they'd have provided a manual of some sort (e.g. the "Great Invasions" devs posted a full beta manual on their website). Even for an experienced SEIII/SEIV player, there are a lot of questions. I hope now that the demo is out the beta testers are allowed to answer "how does it work" (or "how is it supposed to work") questions...
My biggest beef with SEIII/SEIV was in the diplomacy area - specifically the inability to defend your territory from your "allies". In SEIII, once you signed a treaty whereby combat didn't occur if you were in the same sector, the AI's colony ships would swarm into your systems and colonize anything they could. They also had a tendency to sign such a treat, spend a few turns penetrating deep into your empire, and then Pearl Harbor you. So, I always had to keep it to "non-aggression" or war and garison the border warp points. It kind of felt like Rome vs the Barbarians. I thought SEIV would fix that with the ability to clain systems and negociate ownership, but the AI turned out to be automatically programmed to claim any system adjacent to one contailing their colony - even if a few turns earlier they had dropped their claim as part of an agreement with you. So, Rome vs the Barbarians again.
I like the custom treaty system in SEV. A question I have is relative to the treaty element "can colonize each others systems" - does this mean unless I make such an agreement they can't, even if I have all sorts of alliances with them otherwise? Also, I don't see a mechanism to claim a system - what makes it "mine" from the standpoint of that treaty element? Also, I have one race in my game that just seems to ignore diplomatic proposals - no answer at all - bug or feature? How does the AI react to getting beat up? I mean if I thrash his fleet is he more likely to agree to my treaty proposals because he's intimidated, or less likely because he's angry?
Some aspects of the GUI are actually improvements, BTW. For example, I like the ability to create custom reports, the ability to save & recall build ques & that I can now upgrade ships while they are still in fleets.
On the subject of upgrades, now that higher levels of a given hull type are available (e.g. larger sizes of Frigate with each level of the applicable tech), I think this could have been used for a more effective limit on upgrading that the cost rule carried over from SEIV (which never stopped anybody, just made you go through several upgrade steps). My idea is just don't allow a ship to upgrade to a design that uses a larger "level" of hull that it has. You'd need to ability to upgrade designs without upgrading the hull level, but that wouldn't be a big deal. Eventually your oldest ships might have the latest tech, but would be significantly smaller & less capable than newer ones (more or less how it works in real life).
On the subject of ship design, that is a place where I do admit the GUI needs a little work. I'd like an SEIV-type collapsed view so I could see at a glance what was on a given design. Having the level of the system superimposed on its icon as in SEIV would also be nice. Having the boxes aranged on an outline of the ship is visually interesting, but unless the decks actually mean something in combat I'd prefer to get just three rows of slots/boxes - armor, outer hull & inner hull. The collapsed view should show those separeately, since it does apparently matter.
One thing that I find odd is that (so far, up to light cruiser) level 5 of a hull type uncovers the tech for the next hull type. The odd part is that a level 5 frigate hull and a level 1 destroyer hull have the same volume, but the destroyer has more crew & life support overhead, so the frigate ends up more capable! That doesn't seem right. The starting point for a given hull type should still be bigger than the prerequisite level of the next smaller hull type (easily modable, though).
I like the new system-wide function of Resupply Depots. I think that will make maintaining warp point pickets in your own systems without all the micromanagement (in my game so far my fleet is too small to afford to park ships, though). I find the separation of supplies & ordnance interesting. I can envision large scale offensive operations requiring a considerable fleet train of logistics ships - especially if you use a lot of ordnance-intensive weapons. Somebody up-topic mentioned how their fighters sucked their carrier dry of supplies & ordnance - sounds like something you need to allow for in carrier design (real life carriers devote a lot of internal space to that). Again, my fleet is still too small to have to worry about it, but can you directly transfer supplies & ordnance between ships? Do ships in the same fleet share?
Only one battle so far. One of my exploration Frigates mounting a 1st generation missile launcher (or maybe 2) popped into a warp point defended by a gaggle of Depleted Uranium Cannon-armed Frigates belonging to the race mentioned above (the one that won't talk - in fact this was "first contact"). I was quickly wiped out, but went back to my previous save & tried again a few times to get the hang of the combat system. As it turned out, the gaggle were all either the same speed or 1 slower than me, so if I took off immediately running away they could not close to within weapons range (the range rings are cool). I could let the lead guy catch up to my missile envelop, then run again while pounding him - three broadsides => mission kill (speed <4) - wait until the next guy passed the first & repeat. Unlike SEIV, there is no corner to catch you. After I got the last one, I probably had insufficent odnance to actually finish any of them off. So, I tried circling around back to the warp point to escape, but the combat ended before I got very far along on that plan. It seems like a design strategy of the highest speed & longest range weapons will mean that the worst that can happen to you is a stalemate (if the other guy has lots of point defense). I'm not sure that's a good thing, but that was SEIV, too. Now you have to worry abount running out of ordnance, though. Of course, stalemate isn't good if you are on the strategic defensive...