I'm not sure whether this answers Ben's questions, but i use the free version and from time to time I run into spots where the image resolution is fabulous (just to be sure, I checked EDDN too right now).
I made a brief comparison with MS Live Maps for a few reference locations and IMHO GoogleEarth gets a higher "score". My first concern is having an acceptable resolution everywhere on earth, as I need for the world tour.
However, I am not sure whether scenery builders will greatly benefit because, as image spatial resolution is continually enhancing, the TIME resolution diminishes. Or, to say it more plainly, some images are really old.
In the romanian FS forum, someone "discovered" one day that a province airport was rendered on GoogleEarth in high detail. In fact, so high was the detail that some military jets were visible... but local posters wrote that those aircraft were removed from there more than 5 years earlier.
So I suggest GoogleEarth (and probably MS Live Maps too) are of better use for geographical features than city buildings, which change faster than their images
Andrei