Played the game with my brother today, it was his first time so we did a 3 player map, 2 vs 1 normal AI so I could talk him through the game and he could have a little fight. (Hadn't realised how much easier Normal was than before but never mind)
He played on High, DX12, on an AMD GPU.
Bug 1: He would get some odd graphic effects on the map (not just the purple around the edge) and odd glitching on some of his units, he said it looked like it was flickering between different LOD textures models. (On a side note I don't think you have your LODs balanced quite right, even when working well you can tell the higher model and simpler model swapping too easily even when viewing a T1 unit from a little ways out)
Bug 2. He built a T3 factory (substrate) and tried to build the Assault T3 and it appeared but did not build nor could it be helped by engineers. He built a 2nd factory and the exact same thing happened. He built a 3rd factory and chose the support carrier instead and it worked, those its textures had the problem mentioned above. This is like an old bug but I thought it has been fixed, plus it happened twice in a row so not great.
Fresh perspective 1) Very soon he wondered why the yellow connecting lines did not change to the player colours when nodes were captured. They do in the strategic map but not on the main map. I have to admit it never crossed my mind ha, but it was obvious after he said it and it is a good way to see if you have lost one when you might have otherwise not noticed.
Fresh perspective 2) When mousing over enemy units the cursor did not change at all, he found it very odd/disconcerting and wasn't sure his attack commands were being responded to. Again I didn't see it as I'm so used to how it is.
3rdly, and certainly an old one, he noticed his units didn't respond when getting fired at from things which had a longer range. Obviously you don't want units to run off on their own and get picked off willy nilly, so an aggressive stance and a more passive stance option would be useful to be able to give to troops. In Starcraft do they run forward a bit and then retreat? I forget.
Anyway, just thought I'd mention some things from someone new to the game. There were a few other things, like the radar coverage was too small based on the description but I showed him it could be upgraded. Also, although the AI spread down to him it only ever sent troops against me. I sat in my corner for quite some time just holding the AI at bay while he got to grips with things and hoping he could have a bit of a fight but they never sent a single unit against him even though it was an artificially long game. I had by far the largest score and was a little closer so perhaps the AI is programmed to go for that opponent exclusively but he thought it should have been able to fight a bit on two fronts.
We'll try again tomorrow to try out orbitals, but with DX11 so he can check FPS, and also I told him the bugs won't be in the DX11 version 
One of my own observations from watching. He attacked a position with a bunch of T1 and the drone carrier T3. The position had various point defence including one PHC AA tower. I just zoomed in to watch and that single AA tower seemed to be able to completely dominate/nullify the T3. The drones would just blow up in big clouds, some would come back in and the same would happen again. It seemed to me that the AA tower was perhaps too effective against the T3.
