2.1, beta 4) has been seeded to developers, but takes one crucial element off the table -- push notification. If you'll recall, the new feature will allow third-party developers to take advantage of Apple's servers for real-time push of data to applications. Apparently, the feature has been cut from the most recent beta for "further development" with no indication of when it will be reinstated. Of course, this is a beta seed of the firmware -- the actual release is slated for September -- and it makes sense that Apple would be tweaking major additions like this before going live, especially considering its recent launch debacles.
[Thanks to everyone who sent this in]