I imagine Apple engineers are already working feverishly to patch the security hole- and not just because they aren't keen on jailbreakers. The exact PDF vulnerability, if it becomes known, could potentially be used by less magnanimous hackers to install malware onto your device. Interestingly, comex has also released a tool called PDF Patcher 2 that allows jailbreakers to patch up the exploit. Locking the door on the way in, so to speak.
Apple is serious when it comes to security, so I imagine we will see a quick fix of the PDF exploit (and thus JailbreakMe) in iOS 4.3.4. Because of this, comex advises JailbreakMe users to save 4.3.3 SHSH blobs with TinyUmbrella if you'd like to keep your device hacked when the next iOS update is released. And as always, remember to sync and backup before jailbreaking!
Mike Keller is GeekTech's resident iOS Developer nerd. Catch Diary of a Developer every week here at PCWorld's GeekTech blog.