I use Google Earth a lot for flight planning. I often need to find places to land around cities and Google Earth shows me where potential helipads are (Parklands, school ovals etc). The lat long is accurate so I get the lat long off the screen and punch it into the gps, couldn't be more simple. Makes me look like I know what I'm doing when I get there!
It's also handy for measuring distances. I often fly interstate empty just to ferry people from functions back to their hotel, using Google Earth I can give them an estimate of the time it will take. The shortest flight back to a hotel I've done was 55 seconds and it was a 9hr ferry to get there!
CH