Just added to DAP is a new page of examples with the Leica 24mm f/1.4 Summilux-M ASPH. I have also added a lens review page with working notes on my experience with it, to my Guide and Review of the Leica M9. Its very similar to the 21mm f/1.4.
The 24/1.4 is about $6495 + $759 for the M-24 viewfinder. Like its 21mm f/1.4 sibling, it’s a lovely lens. Leica offers three 24mm lenses: f/1.4, f/2.8, f/3.8. Which one is best for you should be clear from my Guide, though price might well be the factor that decides the issue.