I'm running Lion 10.7.4 and, as i said, it runs just fine on my PC. But 32-bit only, so no Finder and other 64-bit apps (even my CPU being a 64-bit capable CPU; ssse3 is crucial for Lion to support 64-bit apps on 32-bit mode).

With Mountain-Lion, as said in various places, including here, we'll definitely need a ssse3 emulator for non-FX CPUs, but even that won't be enough: until now, we couldn't get a Lion 64-bit kernel to work on AMD CPUs, even Buldozer ones; the maximum we got was 64-bit app support, only on Buldozer CPUs. To run Mountain Lion, we've got to do better than that: we'll need a 64-bit kernel and the ssse3 emulator (a static one, easier than the previous on the fly sse3 emulator, but still no easy a task) for the non-FX CPUs. So the mountain to climb is high indeed.