I have been looking around for a flash to use with my G2 (and GH2 when it arrives), and wondered what input people here might have on the Panasonic FL3600 and FL500. The FL500 seems like it might be a bit large on a m4/3 body, so I am interested in what people's experiences are with either flash unit.
The FL3600 and FL5000 are re-branded siblings to the Olympus FL36 and FL50, which have both been superceded by FL36R and FL50R models. (The R stands for "Remote", meaning these updated flash units can be used in dedicated-wireless-remote mode with Olympus bodies supporting the protocol. Panasonic does not yet support the dedicated wireless protocol.)
They are all very good flash units: well made with a good feature set and reasonable power.
I've been using the FL36 with the G1, L1, E-1 and now E-5 bodies since 2007. It's a nice size and weight for the G1/G2/GH2 bodies and has satisfactory power for most uses. If you're going to be considering extensive use of light modifiers or need more power for larger spaces, the FL50/FL5000 is the one to get as it has substantially more power.
There are also a couple of Olympus-FourThirds dedicated flash units from Metz that can work well with the Lumix G cameras according to others who have used them, but I have no personal experience with them.