Unless you have a very specific use case, I personally wouldn't bother migrating App Data, only some applications will work gracefully by moving it and honestly a lot of it just isn't useful. Move Documents, Downloads, Desktop, Photos and Pictures into the new profile, if you do it while logged in as the new user you won't need to worry about permissions (you will need to grant access to the old profile to the new user/use your domain admin creds/or temporarially make the user a local admin) and reconfigure things like outlook, etc manually.
Having said that, Outlook and sometimes QuickBooks do store data there. If your user is storing email offline (old POP account, they set up an archive, or if they have a previous company/employee's PST) you will need to pull that out of the App Data folder and attach it to the Outlook profile. Bookmarks and favorites will also need to be moved manually, but that takes <10 seconds.
Before you leave, have the user launch the applications they use regularly and ensure all the data they need is there and don't delete anything for a couple weeks to give the user time to figure out if they are missing things.
Good luck with your migration!
