As you can tell from the version number, it is a minor update that mostly concentrates on bug fixes and performance improvements. You can expect faster camera focusing and fix for the data dropping issue that plagued certain devices.
The update also brings along a new dialer app with major UI changes and a new contacts app with some minor UI changes.
The update has started rolling out now and should be available soon.
It is weird I have a nexus 7 (2013) and have not gotten an update. My mother's tablet a nexus 7 (2012) wifi has gotten the update. It doesn't look that much of a real update so it is fine.
Meh. I just want my Android 5.0.