1-Notification Center: you can get many ones similar to it from Cydia . This includes lockinfo, mobilenotifier and notified pro.
2-iMessage: there are lots of chatting apps available in the AppStore , but I think apple needed it to knock blackberry out. I recommend Whatsapp because it is an easy to use application and allows chating on multi-platforms. For example iPhone, Blackberry and Android,
3-wifi sync: there is an app in Cydia called wi-fi sync which enables wifi sync just like iOS 5.
4-editing photos: there are lots of editin photos apps on the AppStore . I recommend camera+ .
5-deleting calls from recents: this feature could have been enabled by downloading a tweak from Cydia since iOS 2. Then apple put it out in iOS 5.
6-photoalbums through iPhone: I think this is great. Creating, editing and removing photoalbums without the need of a pc. But apple were a bit late since this tweak was available in Cydia before iOS 5.
Even though these features were available before iOS 5 I think it is great that apple enabled them by default in iOS 5. Anyway, apple needed these features to keep its reputation up.