Examples I've seen of the 25 Summilux have been impressive, as well as the 25/2.8. However the 25 is pretty big. Samples here including shots of the lenses on the G1.
http://dc.watch.impress.co.jp/cda/review/2008/12/11/9815.html
I've owned both the Nokton and the Summicron-C, and liked them both. Some people don't like the Nok bokeh, although like any lens bokeh depends on so many factors. There is a ton of info on the Nokton here, including comparisons to the 40 Summicron-C. My only beef with the 40 Summi is the oddball filter size. They are getting more difficult to find for reasonable prices. I think it is an underrated lens, but perhaps this is changing as reflected in the price increases.
Another 40/1.4 is the Olympus Pen F lens, which is even smaller than either of the other lenses, although maybe harder to find.
http://dc.watch.impress.co.jp/cda/review/2008/12/11/9815.html
I've owned both the Nokton and the Summicron-C, and liked them both. Some people don't like the Nok bokeh, although like any lens bokeh depends on so many factors. There is a ton of info on the Nokton here, including comparisons to the 40 Summicron-C. My only beef with the 40 Summi is the oddball filter size. They are getting more difficult to find for reasonable prices. I think it is an underrated lens, but perhaps this is changing as reflected in the price increases.
Another 40/1.4 is the Olympus Pen F lens, which is even smaller than either of the other lenses, although maybe harder to find.