First time posting in the forums, but just had to mention that I was having the same issue -
Recovery Mode (if you don't know, Google it) and downgrade back to iOS6, then Restore your iPhone from your iCloud backup, and Shift/Option + Check Upgrade and Select your File. Worked like a CHARM!
THANK YOU!!!! Hope this helps anyone else!
I'm a registered developer and have been using the iPhone 5 I'm trying to upgrade a development device. I've entered DFU mode, but am still getting an "...isn't eligible for the requested build." error when trying to restore to 6.1.4. Did you encounter this error, and if so, how did you get around it? Thanks!
FWIW, in order my iPhone 5 to 6.1.4, I only had to put it in DFU mode then click the restore button in iTunes. Both times I did it, iTunes would say the restore had failed. The phone would then have a progress bar that would not progress. Putting the phone back into DFU mode and running the restore a 2nd time would work.
I've now restored my iCloud backup, and will do the option-click upgrade method, and report back.
[update] This morning the update method worked perfect (didn't try the restore straight to iOS 7 method again).