This week I wrote the PWN2OWN contest taking place at CanWestSec conference. I just found out that the MacBook Air running OS X was cracked! Charlie Miller successful cracked the system by directing Safari browser to a Web site that contained malicious code. No details of the exploit have been made available and they most likely won't be made available before Apple releases a patch.
So that leaves Ubuntu and Vista as targets. My bet is that Vista will fall way before Ubuntu, but time for the contest might run out before either system is cracked.