I would be a little careful
Windows 8 by all accounts is very different to Windows 7, and further it has not been finally released.
Ancestry.com has not had anything to say about FTM 2012, or any other version of FTM for Windows, eg FTM 2011, FTM 2010, etc and Windows 8.
I have no idea if there are any changes that need to be made to FTM to get it to run in Windows 8
I would suggest caution until there are some clear advice.
In the meantime FTM runs perfectly well in Windows 7, Vista and XP
I would not rush it as there seems to be a lot of risk and no gain