Apple has released iPhone firmware version 1.1.4. Though anticipated by many, the release of the new firmware has not coincided with the release of the iPhone SDK. Instead, the apparent reason for the release of the new firmware is to resolve bugs caused by or left lingering after the release of iPhone firmware 1.1.3.
As always the new firmware is available for upgrade through iTunes, or via direct download from Apple. Users upgrading via either method should always make sure their iPhones are backed up before beginning the upgrade process.