On loan from Leica I have the 21mm f/1.4 Summilux-M ASPH and 24mm f/1.4 Summilux-M ASPH. I like both lenses already. However, my M9 is showing consistent backfocus with the Noctilux f/0.95 and these two f/1.4 lenses, and might have to go to Leica to be adjusted.
Both brilliance and color of the 24/1.4 and 21/1.4 Summiluxes are superb— they are modern designs that work well on the M9, with great control of vignetting and color shading.
My personal favorite so far is the 21mm f/1.4, because it would make a great complement to a 28mm f/2 (though I own neither). The increased versatility and superbly uniform coverage by f/2.8 make the 21/1.4 a winner (ditto for the 24mm f/1.4). And quality at f/1.4 is very high, provided that you focus it accurately (not easy).
I’ll be reporting on both lenses in detail in my User’s Guide and Review of the Leica M9 once I have focusing issues sorted out.