CGretired,
I have one of the GP Balance Machines and I really like it. I think that it is worth the money. The nice thing is that when the plane is on the balance you have your hands free to hold the plane, add weight, shift the plane, or whatever else needs to be done. Plus, when I get the plane balanced I leave it sitting there for a few minutes just to be sure. It's actually one of the tools that GP sells that is worth the money. You can balance on you fingers (I still do that at the field all the time) but the machine makes it a lot easier.

Hope this helps

Ken