Late response but...

I have a GH2 and have 3 Metz 58 AF1 flashes. They have a Panny/Oly/Leica compatible version. They throw out an incredible amount of light and if you patiently hunt on eBay you can get one for less than $300.

When using it mounted on a camera's hot-shoe, I recently learned a great technique at a workshop with Neil van Niekerk. Get a cheap piece of black 8X10 craft foam at any crafts store ($0.99-1.50) cut it into 4 pieces. Take one pice and attach it to the head of your flash so it flags the bottom and sides of the head. When shooting a room or a person aim the head somewhere between 4:00 and 8:00 from where you are standing angled slightly upward to where the wall hits the ceiling. The effect is bounced diffused lights that is more directional and controlled than unflagged ceiling or wall bounce flash with nice gentle contrast. I've started shooting some headshots with this and the effect was closer to an off camera softbox than to any other on comer flash or ceiling bounce I've previously used. Off camera flash with modifiers is still better but this technique changed my view that camera mounted flash was only a last choice out of desperation.