1.) It takes ages to unmount an image, even with discard. Surely this should take no time, there isn't anything to write to the image ?
2.) Shutting down a machine with a wim attached leaves stray stuff around that it's really difficult to delete. Even the cleanup-wim option seems confused.
3.) It somehow manages to screw up ntfs-3g in Linux. Nice. It's gotta be bad to mess up Linux.