Mostly an FYI after struggling to solve a few issues:
1. If you decide to use Microsoft OneDrive, be aware that it will set a lot of your common user folders to ReadOnly access for individual users. I think it does this to properly manage sharing these folders online for permissions, but it really confused me as it didn't let me know. This prevents importing pictures to these folders in LR, but LR4 and LR6 both provide the wrong error message of saying the files cannot be read which isn't true. It really means files cannot be written to the destination folder.
To fix this you need to set your user permissions on the Picture folders to allow full access to undo what the OneDrive features does to these files and folders. I am uncertain what the security repercussions are when these folders are shared via OneDrive, but if nervous, disable OneDrive or move your image store to another non-share location and only put pictures you intend to share into the OneDrive shared locations.
I hate to say how long it took me to figure this out, but I am posting to help others not fall into the same problem. Perhaps someone else can provide more detail into changing permissions (Security tab) and/or what to do in OneDrive, but this should get you started.
2. Uninstalling older versions (LR4 in my case) seems to have done a few minor funky things to my LR6 install. When I launch LR6 I get a "Server Busy" message for several seconds, where pressing Retry a few times until it clears does work. It is just an annoyance. It would be nice to understand what is going on, and how to fix it.