I am almost certain that iTunes and the Photos app no longer use exif data to sort the photos.
My reasons are:
1. My photos are dated and sorted correctly and when I sync them with the samba fix they appear in the "random" order people are complaining about, however if I install the iPhone app it correctly sorts them by exif date.
2. If I copy the photos exactly as is to my Windows machine's local disk and make no changes to the photos and resync them, they then appear in the correct order by file name.
3. If I make the 1 change to Samba to make it return directory listings in a sorted order then the photos again appear correctly sorted in the Photos app.
I think that a change has been made in either photos app or in iTunes between iOS 4.x and 5.x that means photos are now displayed in the order they appear on the filesystem, note this is not always the same as the order that a human might expect.
It would be interesting to see what order the photos appear in iOS but both of my iDevices are now running 5.1 so I can't jailbreak them anymore.