Just downloaded Galaxy 2.0 beta and sync'd (sank...sunk?) all my clients/games and it looks promising. Not sure how to manually add stuff that I manually added to Steam/Origin (mod supported launchers and stuffs). I could see myself using this as I was already one that added lots of my non-Steam games to Steam manually.
I got in also...finally. And yes, it's real nice. Have all your games for the major stores (Steam, GOG, Origin, UPlay, Epic, XBox, PlayStation, etc). Runs smooth, looks great, integrates stats (Achievements, Time-tracking, etc) from other services that support stuff of that sort just fine.
Seeing games you own multiple places (when you don't sort) is cool, as you roll-over a title and it'll say the game's name AND what service it's on - which is a big deal for me. Some services like Uplay, if you buy a game there and it could use only really some other service, it doesn't tell you (i.e. Sleeping Dogs: Definitive on UPlay still uses Steam). I did wish within the picture of the game, in the corner it had the symbol of what service it is on, without rolling over - which would've been even better, since I do own some games on multiple different services (i.e. I own Dead Space 1 and 2 on both Steam and Origin).
Of course, it's still easy enough to just sort by service. You can even add tags here and search by genre, which is great. And you even edit/add tags to add genres or important notes, so you can sort even further.
I also was looking for ways to add Non-Service games (i.e. Retail games or games not tied to a service program-app) - but couldn't find a way either. Is it even in this version?
Regardless - for a Beta, this thing's in great shape.
EDIT:
GOG Rep says Manual Game Adding is just not in v2.0...yet:
https://www.reddit.com/r/gog/comments/cdxbuy/is_there_a_way_to_manually_add_gamesprogram_to/etx71e3/?context=10000