In addition to checking daily for security updates, Mountain Lion includes app sandboxing to keep misbehaving apps from compromising your system, and kernel ASLR for improved protection against buffer overflow attacks.
The difference in this case, experts say, is that the Virtual PC vulnerability is the symptom of a larger problem lurking beneath the surface: assuming that protections such as ASLR, DEP and SafeSEH will always be around to save us.