Is there ANY way I get get this off IMMEDIATELY before all my users find out my WP installation is old?
Do you think your readers are going to throw their hands up in disgust if they know your WP version is out of date? Guess what? They couldn't care less what version you're using. HOWEVER -- if I were a contributor I wouldn't be happy because if I'm going to bother to write something I'd like it to be protected with the latest versions updated security.
Or perhaps you're using WordPress MU and don't want your users to know their blogs are at risk because you don't want to upgrade? If you're running MU it's not just a choice to upgrade, it's a responsibility as far as I'm concerned. Especially if you're charging. I'd be PISSED if I was paying for a service with a lazy admin who doesn't want to give me my moneys worth.
As Michael said... just upgrade!