A new iOS version just can't afford to pay no attention to Siri. Just as the rest of the iOS 7, Siri now looks different. It always launches in full-screen and has a real-time voice graph. Another UI novelty is the option to edit your voice request with the keyboard in case Siri didn't hear you right.
Siri now offers some new voices as well, there is both female and male English US for example.
The most important Siri upgrades, of course, are under the hood. Siri now has Wikipedia integration.
Siri can also carry out commands affecting the iOS - it can turn Bluetooth or Wi-Fi on/off, increase brightness, play voicemails, check other people's social network status, play iTunes Radio stations, etc.
The Maps app surely got some improvements, but even after the update they can't quite measure to the competition like Google Maps and Nokia Here. They are prettier looking though and got a major new feature - the new Maps app offers turn-by-turn walking directions.