Hey all.
I just tried the new version of Google Earth. I am right now capable of checking LOS conditions on Google Earth by going 3D and elevate down and view in the right direction. If you have drawn a line (measured) between 2 points you are able to get a quick idea about LOS conditions. This is an awesome tool and fixed one big problem for me by telling me what was in the way and by elevating up i could see how high further one end should be. You can see the "Eye Altitude" in the right bottom corner. Of course this is not 100% because it only uses GPS heights and doesnt account for trees etc, but it's free and accurate enough for long shots.
Regards
/Henrik