GOG Galaxy is GOG.com's new cross platform desktop client similar to Steam. We've had a nosey at the beta.
Once you're logged in you can view the store which is the same as the GOG.com homepage. You can also view your library, again, it is the same as the GOG.com library area. Clicking on one of your games allows you to install it or any of the additional content purchased with the game.
The app has a settings area so you can decide on the default game location and if you want the app to launch at startup.
The friend system is seems pretty bad, you can't simply add your friend by email or name, you need to find them in the community wish list, forum or game comments sections. This isn't how people manage friends.
The app has a icon in the notification area but only has options to open or exit the app. It would be nice to have shortcuts to games and the friends list here.
The client is a beta and so some bugs are expected. Having said that it didn't seem too bad, occasionally a screen would stay blank instead of showing content or take a while to load. The back and forward buttons don't seem to work very well.
As it stands I can't really see the point in this client, it is just a cut down web browser for GOG.com with a download sidebar and it's not like the GOG.com website is difficult to use. Maybe one day it could rival the likes of Steam but it has a long way to go.