As far as iOS 6 goes, it was pretty much a non-update from iOS 5. I can't even think of one thing that actually changed between iOS 5 and 6...
oh wait, Maps.
oh and they ruined the status bar with that weird flat blue thing.
...
yup, that's about it.
oh
Passbook? I still don't know what that app is even for.
From iOS 4 to 5, however, we saw much larger changes:
- iCloud (iMessage, Mail, backups, reminders, notes, documents in the cloud, photo stream, etc etc etc)
- Notifications revamp
We also see similar big improvements from iOS 3 to 4:
- MULTITASKIN'
- WALLPAPERin'
- AirPlay, AirPrint
- Find my iPhone
I really hope that iOS 7 will see a return to the more feature-rich and I daresay actually *useful* iOS upgrade pattern we're used to. I think we stand a good chance of this.