AppleInsider says that Apple has yanked the Push notification framework from the latest version of the iPhone 2.1 firmware beta. Push got a lot of play during WWDC -- it's a service that will send information to the apps on your iPhone as needed (tweets, for example, will just come rather than having to refresh Twitterific all the time), but apparently Apple doesn't think it's ready for the stage yet. They've wiped it from the beta, claiming it needs "further development," and haven't given any indication of when it might return.
Here's hoping it gets back in there before the expected release sometime in September, but then again, it's not like Apple should be taking any new chances with features right now. From Mobile Meh to iPhone activation problems, Apple's got to make sure that any more widescale releases go as swimmingly as they possibly can.