Easy. If you got from iTunes and not some link off a website, its real.
True for a normal scenario, but mine was locked up and had to be put into the firmware restore mode. I'm not sure if iTunes did a restore with the real or Thursday version. Attempts to do the restore on Thursday failed so my hunch is I have the official fw now... Just can't verify it because the reported version on the iPhone doesn't include the extra identifiers described in the original MacRumors post. Anyway - apps are great but the sync is painfully slow.
Have another issue that I think is coincidental timing...looks like my phone always thinks headphones are plugged in regardless of the visible reality. I Guess whatever the switch mechanism is in the jack is toast. Don't think its related to the firmware.
******************** MacRumors firmware post **************
The official iPhone 2.0 Firmware is now available through iTunes 7.7. The new upgrade file carries the same build number (5A347) as yesterday's early leak:
iPhone1,1_2.0_5A347_Restore.ipsw
The "1,1" designation is different, however. The significance of this difference is not entirely clear. Despite the same build numbers. the file sizes of the two builds are different. For those who are concerned, you will likely be able to crossgrade to the official release using the same technique as yesterday. We'll post details of this after some testing. The iPhone 2.0 Firmware provides a number of new features and also provides support for the iTunes App Store.