I'm running P5 over here w a Win 8 64 bit lap top ..
P 5 itself runs very good as a 32 bit app on it's own in Win 8 64.
It has been very stable for me so far , it is pretty snappy and responsive compared to my former P 5 / XP spec...machine and set up
there is no rewire to X3d 64 bit as mentioned ...
I did a custom install of X3 PE at 32 bits to get some of the instruments and plugs over and into P5 .
a few things that didn't show up from X3 PE as useable in P 5 , all the Nomad Factory plugs , True Piano, Overloud TH2 ,
Breverb , Lounge Lizard and the Pro channel modules
PS, i didn't expect them to show up …..it would have been to good to be true ….
Rapture , Dimension Pro , Session Drumer 3, zt3a+, Addictive Drums , Melodyne single track , and all the Cakewalk PE vst plugs have made it over and are useable in P 5 .
(that in itself blew my mind and made the gamble of doing the P5 install more than worth it to me…..)
all the best ,
Kenny