Great work so far on moving this forward. I am testing this for the first time after I recently noticed that the legacy client will be deprecated soon.
Problems so far:
1) First big problem for me is UPnP. I am getting orange Proxy Connection. I have a working UPnP gateway on the system, and I can watch all open UPnP connections. I have other windows software which is successfully opening ports through UPnP and I can see this on my gateway dashboard.
I would love some help diagnosing this. I am running latest Windows 10 Pro. Steam installed SC:FA, Steam Linked. Latest Downlord client (downloaded today). It is possible the old client was also connecting through proxy.
2) Local Replays looks to have a limit (300) that it can read which is understandable, but it loads them in chronological order meaning all the most recent ones are missing. Ideally it should read them in reverse chronological order.
3) On my Windows Taskbar, the client is showing a continuous green wave. Not sure why.
4) Under 1:1 Ranked Match, I can't tell whether the faction icons are selected or unselected? They go really dim (almost unreadable) when I click them, but I have no idea which state is selected/unselected and I don't see any other indications/tooltip.
5) Under Vault/Maps -- it spins forever... Maybe that is the cause of the green wave?
6) I really really really miss the game.pref link under the main menu. You have Mod/Map/Mod and I can find replay from those, but not game.pref.
7) Launching a 1v1 Ranked match triggers a popup saying there is another match available
MINOR UI STUFF (ignore for now unless you're already there):
A) Scroll bars can't be grabbed if window is not maximized because you get the resize instead
B) Unit database is slow scrolling -- was much faster in old client
C) Remembering my game password (EDIT)
D) Graphical identifier in the game tile for password games (EDIT)
KUDOS
* A working Mod Vault!!!!!

OVERALL IMPRESSION:
The features are all here for me to switch. Not sure whether I like the new game screen yet. Tons of better data for sure I just have this feeling I saw more games at a glance in the old client. Have to try it for a while.
EDIT:
Create game is really nice! Big improvement.