micro four thirds is a 2x crop from full frame. The gh2 has a sensor that is slightly larger than a regular micro four thirds sensor, and because of this, it can use different portions for different aspect ratios. this picture may help.
however, many people ignore/don't realize this, and calculate the crop factor by the physical measurements of the sensor, which leads them to believe it is a 1.86x crop. as far as i know, it is a 2x (because only certain parts are used in each aspect ratio). it took me a while to understand this, because the people at preview are still arguing about it and saying how it affects depth of field etc.