I haven't had any issues with the updater program or the firmware itself. I'm running W8.1.
The only MS-Windows machine I have access to is an ancient XP laptop I kept around for emergencies. The first procedures I tried under VirtualBox- and it didn't work. The next several attempts on the ancient laptop didn't work, then it "bricked" one of the Senas and finally I got it to work.
Really, the whole thing is stupid- one should be able to download an update, and simply plop it on the unit's storage using standard USB storage mode and done.