VSS is pretty great. I use Macrium Reflect on Windows, and it just works. I've never once had a problem restoring a Macrium backup to bare metal, even if it has a bunch of incremental backups.
VSS is great indeed. Very useful to eg. P2V a machine live, even saving the P2V image on the same drive.
But VSS, like LVM or other snapshoting FS, requires dedicated FS support. You don't have VSS on FAT32. Here, blktrace works at block device level, so does not rely on any FS support.
