The combination of the new sensor in the GH2 and some improved JPEG processing on Panasonic's part has resulted in some of the best image quality we've seen in the company's cameras to date. For example, in most Panasonic cameras--even the good ones, like the LX5--the text in this shot is usually riddled with color noise.
That said, there's still quite a bit of noise in midrange-to-high-ISO JPEG shots; I can't confidently suggest shooting higher than ISO 200 in that case. However, using raw pushes that to about ISO 800, depending upon the scene.