Naive. In fact, early adaption often just opens new holes. The earlier versions come with amazing bugs. There are at least two significant holes in the new SP2 firewall for instance. In the meantime, just installing the small 23-026 (or what was it again) and follow up patch (can't remember) was enough to stop the Blaster worm and MyDoom. SP's rarely come with any urgent patching, hotfixes will have been released for those long before that.
The only reason to occasionally upgrade to the next Service Pack is because some software works better with it. But that only happens about a year after the SP has been released, and there is little urgency to upgrade earlier than that, if you ask me.