This will automate game downloads, automatically update your games, let you show off your achievements to your friends, etc. But it is in no way mandatory, and if you choose to use it, you don't have to be online for any offline features.
This is exciting news. I always loved GOG for being a DRM-free option for buying games, but hated the loss of the convenience Steam provides. Steam kinda controls the board in the PC gaming marketplace these days, so I hope this provides some extra competition to make the whole scene even better.
http://www.gog.com/galaxy
Neat! Anxious to see this come about. GoG really needed this, even if only to help keep the game patches updated. I think that the Steam gravity well may be too strong to pull away from, but it will be nice to have the competition.
This is great news. In gaming I look to Steam, Humble Store & GOG for games and anything that makes them better is good news in my book. I really like that out of the three I love, GOG and the Humble Store both focus on DRM free games.