Just went on a big all day cache walk with the GC, and I can say that I love it! It is jumpy when you slow down from a good walk, but at around 10 feet, we are putting the GPSr away and looking.
To add custom coordinates, click on Waypoints on the main menu, then hit menu, select Add Waypoint, then Coordinates. Took us a while to figure that out in the field lol.
To update, go to Here and download the v1.6 update. Follow the steps that the installation provides you, since they are pretty self explanatory. Mainly, you will fire up the executable, then turn on the GC, let it boot, then connect it to the PC. Select "Connect to PC" when it prompts on the GC, then wait for Windows to recognize it. Once it does, then you will continue. It will prompt you when you need to do this and provides step by step instructions.