My install would get to '0 seconds remaining', then fail with the message I posted earlier. I'm now back on my Mavericks install from this morning.
I'd formatted my SSD beforehand, so I was somewhat nervous, despite having backups. Time Machine saved my behind.
Good luck, my friend.
Turns out it had installed, and as jammed at the transition from installation to reboot. I rebooted, and it went straight to the desktop. All updates went smoothly except for one from Ambrosia software.
Unfortunately, I now find that my iMac isn't new enough for the Handoff feature. (There's only two years of backward computability) That is problematic because I really don't see the need for an upgrade without that feature. I'm trying to find a Bluetooth dongle that will solve the problem. Wish my luck again.