iOS 7 was a major update. It looks very little like the iOS we’d grown used to in the several years before. However, it’s going through even more design changes. Nothing major, just little UI adjustments here and there.
It has a new dialer, new keyboard design and a few other things. Nothing should drastically change how you use it.
Still, it just goes to show that iOS 7 is still a work in progress.
You can read more about its changes here: CultofMac