Today I went into town and bought a spare battery for the GF1, since I did not want to pay Panasonic's rip off price, I got a equivalent Energizer battery. Now, I have read of Panasonic being difficult with them accepting 3rd party batteries but guess my surprise when the camera refused to use this battery with a 'This Battery Can Not Be Used' message and there is no way to force the camera to use the battery.
If there is something I really, REALLY hate is locking devices down for no reason and using proprietary stuff to force me to buy the manufacturers own accessories.
So shame on you Pansonic!!! This is NOT how you go about things, either sell your own batteries at competitive prices or allow people to use any battery they want in your cameras.
I HATE proprietary stuff and being locked down for no reason, which I why I would never buy any Sony products for example. I am actually very tempted to return the camera just for this. It certainly is my last Panasonic camera that I bought unless they change their stupid policy.
So while I could recommend the GF1 before, now I can only say stay away from it and any other Panasonic camera until they change this behaviour.