Folder Redirection is a Windows property and it works automatically, So it does also in MC15. The folders %APPDATA%\[library,libraryBackup, Default RAW Cache, Image Cache and Temp] are properly redirected to the server and do work.
The problem is only the thumbnails folder. I think the pathname definition in the registry is faulty. The Thumbnail Base path is set by default to:
[Application Data Path]Thumbnails\. Probably it should be [Application Data Path]\Thumbnails\.
In Windows 7 there are 2 distinct variables for AppData: %APPDATA% and %LOCALAPPDATA%. If you want to keep data local on the client you need to use %LOCALAPPADATA% (usually C:\Users\<Username>\AppData\Local\J River) , if you want to redirect to the server data needs to be in %APPDATA% (i.e. \\<server>\<sharename>\<username>\AppData\Roaming\J River).
Even if you enter the properly redirected pathname in the registry, thumbnailing does not work on the server. If thumbnailing is not supposed to work on a server, then it should go to %LOCALAPPDATA%.
The preferred setting in a Windows7 / Server environment is to keep %LOCALAPPDATA% locally and redirect %APPDATA% to the server, so that roaming profiles are being supported. I want my MC library and data on any pc that I log in.
Now, because thumbnailing works only locally, if I log in to a new pc on the network, MC needs to start building thumbnails for this pc again, which is quite redundant.
Redirection can be set in two ways:
a. Either by group policy
b. manually: go the the folder that you want to redirect, right click and select properties and there you will find a tab "Path*. In Windows XP only 4 folders could be redirected: My Documents, Desktop, Start Menu and ApplicationData (only MyDocuments could be done manually, the others only through Group Policies. Now there is a whole bunch of folders that can be redirected both manually and through group policies, but not AppData itself, only its subfolders Local, LocalLow and Roaming.
Hope this helps.