The Summilux does AF with the GH2, though slowly. Nothing like as bad as the Olympus 50mm f/2 but not as fast or smooth as the 14-150mm zoom. There's a process of 3 adjustments every time and then it locks on. Not ideal but it does work.
However I didn't buy it for ultra-fast street photography or sports but for its legendary sharpness and image quality.
The above was taken at f/1.4. Its pin sharp, with no CA or fringing. Again its a lens that benefits from the GH2 sensor. The Digilux3 was a good camera but its 7MP were never really going to show just how good this lens is.
The point of focus is very sharp, and while the 20mm f/1.7 is excellent wide open, this is better. In fact from f/2.8 to f/5.6 its incredibly sharp. I've only used it for an afternoon but f/4 looks to be the optimum aperture so far.
Its not light, in fact its only marginally lighter that the 14-150mm zoom, but it sits well on the GH2.
Its a bit of an indulgence, but I got a very good price for the Voigtlander and decided to treat myself. I love these PanLeica 4/3 lenses and they hold their value very well.
Whether the future Panasonic m4/3 25mm f/1.4 will equal this lens for resolution and sharpness remains to be seen. But in answer to the question, is this a better lens than the 20mm f/1.7 pancake? the answer is yes for image quality, but no for AF. The 20mm is lightning quick on the GH2 and would be my preferred lens for situations where I need the speed. However when I have the time to wait for the AF the Summilux has enough of an edge to make it worth putting up with.
Images - David and Ann