iOS 7’s Notification Center is useful, but Apple’s made a number of improvements in iOS 8. For one thing, they dropped the ‘Missed’ tab, which was always next to useless. There’s also support for third-party widgets in Today View, as well as interactive notifications and the ability to individually dismiss notifications that are no longer applicable.
They are all good changes, but unfortunately, you need to wait until September to make use of them… that is, unless you have a jailbroken phone, in which case, a simple tweak is all you need to get an iOS 8-style Notification Center today.