No. It's a fresh install with DevPreview after that. There are some threads about it.
If I turn wifi off and phone to Plane mode (phone off) it's the same.
I have a 620 with Amber. With Windows 8 it will last more than 2 days.
With Windows 8.1 it only lasts 6 hours. I have tested with Amber and Black and it's the same.
The phone keeps warm all the time and the battery drains fast.
I can't test Cyan because it's not available for the 620, but I am...
Well I have a 620 (presumably locked to Claro Argentina). I reflashed it with a US-AIO firmware and it is working ok and with Cortana. English US language. That's because the original firmware for Claro ARG doesn't have the US language.