Alternative to DMW-MS1
I have the DMW-MS1 for my GH1, but I never use it. It doesn't provide enough of an improvement to be worth the hassle.
I've found that I much prefer to record audio off-camera and then sync it to the video in post. This means I don't have to deal with cables and I'm not limited by the camera (forced auto-gain, etc.). If you're open to recording separately, then there are lots of options available. I often use a Zoom H1, which is quite small (compliments m43 well) and records good quality stereo. Then I use Final Cut Pro to sync the video and audio files.