Selective focus is maybe the number one way to isolate a subject from the background, often it is discussed how much DOF is needed and how much DOF one get from a particular f.stop - fullsize jpg's after the read link.
Captures at minimum focusing distance of 70cm, handheld, it is VERY dificult to get perfect focus even on the superb evil finder of the GH2, and even with enlarged center area, sorry folks, I still do not see a m43 camera as a alternative to my M9, maybe in the future but not today and not a GH2. (I also don't particularly think "replacing" my M is a goal or need)
Notice the noise or lack of same in the defocused areas, this is the bokeh or quality of defocus, of the lens, it is very easy to see the extra kick from 2.8 to 1.4 (summarit to summilux?) - since this was captured on a m43 camera, clearly only about half of the lens actual fov is available, but I find the lens still render well, and also have to remind myself that the 16megapix GH2 is 25% of the real-estate of the 18megapix M9. Practically speaking the pixel density fo the GH2 roughly equates a M9 with a 64megapix sensor, that is some serious pixels. The GH2 have a impressive pixel density, but is a bit more muddy than the M9, you will find it to be fantastic at base ISO, however already at 800 the resolution seems to fall apart a bit and the file become a bit muddy as the ISO goes further up.
Is it worth shooting a Leica M lens on the GH2.? The short answer is "In my opinion NO".
to elabroate a bit more, as I mentioned before, the pixel density of the GH2 is about like a 64megapix M9, and honestly I think the M lenses don't particulary out-resolve the m43 kit lenses. Combined with the challenge of using a M lens on a GH2 camera, personally I would use my old m43 14-45mm zoom or a m43 prime lens, they are incredible sharp and you are sure to get the sharpest possible images from the GH2 with a m43 native lens... HOWEVER, the M lenses render much nicer, and that is worth something, for art, or movie making.. manual nikon or leica lenses have got to be the ticket on the GH2.