I can't guarantee it'll work flawless for you, but i do have Win 8.1 installed here.is it true the news someone told me that in windows 8 there is not anymore the limit (stuttering) when two monitor/device are configurated with different refresh rates? and so I could configure MP to the extended monitor (the TV) without the Windows 7's cap?
2 monitors: left runs @ 60Hz, right @ 50Hz (I live in PAL country) and i haven't seen stuttering while testing.
Best to try it yourself, but can't really imagine why it would be a problem. You can configure the startup screen in MP Config.
I installed Windows 8.1 yesterday. No problem with 24P , 23,976 Hz. refresh rate on tv plasma (monitor 1 , secondary) and 60 HZ (lcd, monitor 2 , primary) , there was no stuttering or tearing using MP on secondary, but there is an issue with 50 HZ vs 60 HZ. it stutter . Il'try with 50 Vs 75 Hz. later.
there is an issue with Windows 8.1. If a pin media portal on start page I've no problem, media portal starts in desktop mode, also if I start it from desktop but I use LM remote keymap to start MP with a script to handle the monitors, switch them enter MP and back on exit and handle the audio card to switch by code from a device to an another (speaker & digital output, do you know ssd audio switcher? http://funk.eu/ssd/ it work fine).
So the problem is that: I'm on start page, MP start but I'm in metro interface/start page, when I start, MP don't switch to desktop mode. It would be fine an option to force desktop mode