I had some issues getting the Witcher 3 expansions to install.
- I played the main quest in May 2015 and I waited until Sept 2016 to play both expansions.
- When I loaded up GOG Galaxy, having not used it at all during that time, it automatically started downloading about 10GB of Witcher 3 content. I assumed it was patches, but figured it could include the expansions as well.
- After it finished installing, I bought the season pass.
- Nothing else started downloading, so I loaded the game. Nothing appeared different, I checked the list of installed DLCs from the menu and saw no mention of the expansions.
- After about 5-10 minutes of Googling "how to install Witcher 3 expansions", I happened to notice 2 new buttons had appeared on my GOG Witcher 3 page to download the expansions (they weren't there when I started Googling because I had thoroughly looked all over that page for any kind of install options).
- I clicked the first one, and left it downloading.
- After a while I checked back, it had finished downloading the first one, but I had to manually click the second one to start that downloading.
- When that had completed, it was quite late, so I needed to go to bed.
- Next day I loaded the game and saw no evidence of anything being different, including on the list of installed content.
- After another 5-10 minutes of Googling I noticed 2 new buttons had appeared on my GOG Witcher 3 page to install the DLCs (they weren't there before).
- Again, I had to manually click both to get them to install.
- After loading the game I finally saw a different menu screen, several popups telling me how to start playing the expansions, etc.
Overall, I was not impressed. Every time I've bought DLCs through Steam, they've always automatically downloaded and installed immediately, without me having to micromanage every step of the process, and at no point have I ever started to worry about "shit, has my purchase actually been made properly? What is going on here?" like I was starting do during this situation.
On the plus side, I've played Witcher 3 and its expansions for around 150 hours with no in game problems, crashes etc, caused by GOG Galaxy.