Hello, everyone. We are currently planning on releasing 1.05 tomorrow. As part of the 1.05 patch I am going to be making some (somewhat) significant changes to the Pillars of Eternity depot structure in Steam.
A depot is a collection of files that we can assign to different packages. When you purchase a game off of Steam you are actually purchasing a specific package that is a collection of depots. The depots contain information about where to place the files from the Steam servers to your local machine.
The reason for this change is because we originally set up our depots so that there was a base depot, and a depot for each OS. Depending on your OS, you would receive the base depot and the depot for your OS. We thought this would work out, but due to differences in the Mac build it is difficult to maintain and will become more difficult with more content being added. The solution is to move the files that were in the base depot to the OS-specific depots. This should be a one time thing as this new structure will scale well in the future.
We have done testing on our new depot structures, but due to how Steam works, we won't know if everything is perfect until we push the changes live (which we are coinciding with 1.05).
The practical effect is that you shouldn't notice much of anything change. The depots just tell Steam what to download and where to put it. Since the new depots aren't changing any of that, you shouldn't have additional data to download (past the normal patch data). It is possible that Mac may try to download additional data for a 30 - 40 minute period in the morning (until the full changeover is complete), but we will try to minimize that.
Thanks for your (future) patience.