So I pushed through the technical issues and played quite a bit yesterday.
General Impressions:
Moment to moment gameplay is fun. The combat can be quite challenging when you're not overgeared. When you start getting a build together, click with the movement system, and utilize the combo systems, it really shines. Can't say much about the story as the missions available are more of a side story than anything with major implications and that's fine. The conversations with NPCs in Fort Tarsis are entertaining. No idea if they actually matter in the long run or not.
It definitely needs some improvements though.
-Flight controls; Swimming controls. These have supposedly been addressed but not in this build. We'll see I suppose.
-UI Readability is poor. This has also supposedly been addressed.
-Objective Markers. This could technically fit with UI readability I suppose but it's not HUD. It can be extremely difficult at times to see where your objective is or how to progress the current objective. The Echo collection objective in particular is very obtuse and confusing if you haven't seen it done before your first attempt.
-Swimming. I mentioned the controls already but I'm mentioning it again because swimming is the worst experience in the game. You can't see anything. Control is terrible. And there are progression points that your group can be stuck behind if a single person can't figure out the path (which is common).
If they can get those issues squared away and obviously get the technical problems addressed, then I think this game will do quite well. There looks to be plenty opportunity for build diversity, customization, and the combat is both fun AND can be frustratingly challenging (room to appeal to different player types). I could definitely see myself playing this alongside The Division 2 and Destiny.