Username or EmailPassword
Windows re install ? Ouch. Although I assume you mean a system restore from an external backup, which doesn't take that long and is less painful.
The notifications are the most welcome change but a very significant one is iMessage. Yes Skype et al do the same thing but they're not as integrated. Nice jab at the carriers.
Here in Spain carriers only gives us unlimited headaches.
In the US we totally pay through the nose for text messages. I pay USD 25 a month for an unlimited text plan for the family. Using iMessage I can go down to a basic plan which costs only USD 10 so this one app would be a huge savings.
(Needless to say, this only applies if your family members all have an iPhone which is probably the whole reason for this app, to lock in the whole family into iThings.)