Apple's iOS 4.3.1 is available for download now, but if you're not experiencing any of the problems listed in the bugfix changelog, I'd suggest you wait. Reason: Jailbreakers haven't verified whether Apple has changed any of the underlying structure or not, meaning, a jailbreak for 4.3.1 might be much further away than a jailbreak for 4.3. But if you don't care about jailbreak, go ahead and grab it now from iTunes.
DISCUSSION
I'm a bit unclear about why one would bother at all with an update when jailbreaking. Does the update provide something that cannot be done through the hack?