As already noted there is a YouTubePlugin still present for Safari though it is not yet activated.
There have been new references found to: 'HeadsetBT HeadphonesBT’ which suggests that in addition to mono headset support we may see stereo bluetooth headphone support.
iPhoneHellas also found references to ‘RoleGps RoleRemote RoleA2DP' which could imply GPS navigation.
A reference to "Google411," associated with Google Maps, suggests the iPhone will receive a directory lookup link for given locations.
The site also notes there is "Printers" in / Library…
Most notably Apple may be taking steps to prevent unlocking. The quote below indicates that the phone may eventually refuse to unlock itself for use with unofficial carriers.
Ignoring request to unlock because we’re blocked or bricked'
Finally iPhoneHellas notes that all records regarding Nike+ have now been deleted in the latest beta.