Apple has released its fourth update to the iPhone Software Development Kit (SDK) beta, which adds OpenGL ES support to the iPhone Simulator application, amongst other improvements. The new release, which is available as a free download for registered iPhone developers from the iPhone Dev Center, is a 1.15GB download, and is listed as build 9M2165, beta 4.
Apple has posted complete release notes here. We will update this story with any new information we discover.
Update: Following installation of the updated SDK, we have found it includes an updated build (55) of the iPhone Simulator application, which is running an updated version of the iPhone OS, version 2.0 (5A258f). In addition, the Contacts application in the iPhone Simulator now features a search bar at the top, which was previously revealed in the iPhone 2.0 Enterprise beta.