If you're one of the millions of iPhone users who've jailbroken their iPhones or iPod Touches--the desktop hacking trick that allows you to use non-Apple approved apps, access the iPhone's file system, and other tweaks--you'll want to hold off on the latest software update (3.1) that Apple announced Wednesday. Updating your iPhone or iPod Touch will break your jailbreak, meaning any services and apps you've installed via Cydia will be gone, as well as Cydia itself.
The Dev Team is working on a new app to jailbreak the current version, but no word yet from them on an expected launch date. That being said, the Dev Team traditionally has had a jailbreak method out within a few weeks of a software update.
Since none of the features of 3.1 is stand out "I have to have it now!" (OMG! Bulgarian keyboard!) you're better off downloading it for now via iTunes so you'll have it handy when the jailbreak software is out, which we'll tell you about here, naturally.