I run FTM 2012 on a 6-core machine running 64-bit Win 7 with 8 GB of RAM. Yes, the FTM application's load time does take longer after the last update. But, once it is loaded, performance has greatly improved. And, FWIW, I don't use any of the sync features.
Vista was a dog of an OS and one of Microsoft's biggest black eyes, so I would never recommend anyone go from XP to Vista. Even on older machines, Win 7 outperforms Vista. The greatest hurdle there is finding drivers for some of the older hardware. I ended up having to ditch an old scanner but that wasn't a big deal to me at the time. For most hardware, the drivers that Win 7 installs work fine.