As revealed by Craig Hockenberry on Twitter shortly after today's iPhone OS 2.2.1 update: developers hadn't heard a whisper of this release, no beta, not even a warning, and it wasn't compatible with the previous SDK. Nice, Apple!
It should come as some relief, then, that the iPhone SDK has now also been bumped to 2.2.1. Says Ars Technica's Erica Sadun:
In all likelihood, the 2.2.1 SDK is, as suggested, a simple bug update without any significant API changes.
So not much different from the iPhone OS 2.2.1 then?
Of course, with such a minor point release we can't really expect anything revolutionary (we'll likely need 3.0 for that). But Apple has been known to sneak some early clues into frameworks, so hopefully we'll find something to look forward to once the deep code divers get through tearing this one apart.