I used it pretty successfully to do Windows 10 activations on systems that weren't going to be upgraded immediately - pull the current drive, slap in a temporary drive with Windows 10 preinstalled and some desktop shortcuts (to retrieve Win8 keys from BIOS, direct link to the System control panel page, etc.). I had a few where I had to tell it to reset Windows which is basically a reinstall, but for the most part it was "drop in drive and boot, Change Product Key, enter correct key from BIOS or sticker, activate, shut down, return original drive, on to the next."
My primary "temp" drive was actually an old notebook hard drive that had been replaced with an SSD, it probably would've been faster with an SSD but I didn't have a spare one handy when I first set it up.