It's nice and I like the improvements. The new camera software features are nice with new filters and I like the new way the photos are stored and grouped together.
It's easier to manage multiple running apps at once by double clicking the home button.
I played around w/ the maps app and it's better, especially w/ the voice command. However, I still like the Google map app better.
Safari's navigation between web pages is better and easier to scroll through multiple open pages.
iTunes radio is cool, similar to Pandora and I Heart Radio, but I actually like it better.
The control center is nice and is accessed by swiping up from the bottom of the screen even if you have an app open. This makes it easy to make settings changes w/out having to close an app, go to settings, etc... However, you may want to prevent access to the control panel on the lock screen to prevent thieves from turning off your "Find My Phone" feature. This can be done in the settings/ control center and turn off "Access on lock screen."
You can have apps update automatically in the background, which is convenient, but probably will drain your battery more since your phone will constantly be checking for app updates.
The mail app hasn't changed much, mostly layout and navigation changes that I like a little better.
I'm sure there's much more than this, but these are the items that really stood out to me. I haven't noticed any battery life changes on my iPhone 5, but I suspect that it's a little less than before iOS 7 and mainly due to the auto app updating I mentioned above.
I'm starting to play around w/ some of my client's new iPhone 5S devices and so far I like some of the hardware changes, especially w/ the camera and the speed of the phone. Not sure I'll get a 5S since I have the 5 so I'll probably wait for the 6.