Google Earth 4.3 was released on Wednesday, April 15. The biggest changes for most people (not power users of course) is a revamped navigation control and much different lighting on the planet.
The new lighting makes the Earth look much brighter, and the orientation of the light can be changed by moving the position of the Sun based on the time of day. This does not really make Google Earth better, it just makes it look different than in the past.
The new navigation control takes some getting used to, but it does let users move in ways that were not really possible before. There is more of a hover mode that makes is easier to move around when you are zoomed in close to an object, such as a model. This is a much bigger deal to me. Google Earth has always been good for navigating on a global scale, but needs some better controls for moving around a regional or smaller scale.
I had some problems with Google Earth locking up on me. I am staying with 4.2 until the next release, which typically cleans up a lot of issues.
Much better write ups on new functionality and a video can be seen at Google Earth Blog, and at Google LatLon , with some nice general thoughts at OgleEarth.