In a recent USA Today.com article, entitled Unprotected PCs Can be Hijacked in Minutes, the authors demonstrate both how important patching is, and the value of firewalls! The article also demonstrates how hostile the Interent can be.
The study ran for two weeks and looked at how vulnerable certain types of systems were, both to being attacked, and to being attacked successfully. The XP SP1 and Mac OSX systems were attacked at about the same level (340 attacks/hour), with 9 succesful XPsp1 attacks, and none for the Mac, or the systems running Linspire (Linux),and XP SP2 with the Internet Firewall enabled.
If this doesn't demonstrate how important it is to keep up to date, I don't know what does!