Summed up: It kicks ass.
No, it does not have all the features of Google Maps/Earth (such as Street Views,) however it looks far better, particularly with “Bird’s eye” option enabled. I was amazed at how good it looks. We’re talking crisp clean very detailed photos you can map with.
I will be doing a video on this soon showing what you can do with Live Maps. There are both pros and cons. Stay tuned for it.
One final note: Notice the screen shot was taken with the Firefox browser. Yes, Virtual Earth 3D works both in FF and IE (but not sure about Opera, didn’t test on that one.)