Thought I'd share this as it came up with a customer during a POC.
They wanted to redirect their Desktop but then when they wanted to copy something to the Desktop, they couldnt just use the %userprofile%\desktop as it had been redirected. Simple enough to fix but then they keep changing the Home Drive (where the Desktop is redirected to) depending on the location where the user logs in (E.g. If they login in Sydney, their home drive will be SYDXXXXXX\Home. They have enabled replication between all sites). Microsoft use a variable called %DesktopDIR% to handle this but its a session variable.
Solution was to check the Site detail and user login details and create a session variable for them to call throughout the config.
Easy fix to what was initially going to be an interesting problem.
I will add that we had to create this condition check for all the sites (55 in total) but there wasnt another way in this instance. (Maybe a feature request to handle this moving forward?! :) )