You can read all about the Leica M9 at Ken Rockwell or Steve Huff who have vast amounts to say about Leica cameras and lenses. I confess I bought it out of curiousity; why does it cost so much? is it worth it? why is it so special? is it special? I'm not an expert. I bought a Canon 7d and a Leica M9. The Canon seems massively superior in every way, and it's much cheaper. My conclusion to date is that the Leica M9 is more of an artist's tool whereas the Canon and other high technology, high end digital cameras are total solutions.
If you are reading this you will already know that the Leica is a rangefinder and is a manual focus camera. It is much easier to set the aperture, exposure etc on the Leica but that doesn't justify the huge cost differential. Leica lenses are very expensive and you don't get one with the 5k body, or a carry case, or even a memory card (you do get a battery). You also need to use Apple Aperture or Adobe PhotoShop Elements or Apple Iphoto because the massive 17.5MB RAW DNG files need a proper media import tool and not the standard PC software. You start to see things differently when you use an M9. You see depth of field, interesting details, colour fringing, good light and many other new things as you go through your daily chores.
Everything becomes a potential M9 subject. Forget using a flash. Leica lenses can 'open up' and see better than the human eye. You can shoot your girlfriend in her underwear by candlelight without a flash and you will get great pictures if you can focus. You might need to wear your specs to focus correctly.
I now use my Canon 7D with a massive Canon telephoto f2.8 lens for wildlife and the Leica for interesting creative shots of just about anything. Leica M9 is really for close shots like portraits, details etc and they are not for zoom, telephoto or any of that stuff. OK, that's enough for now.
If you're into HDR then the Leica M9 is perfect for this technique - see my customer image.
PS - remember to to remove the lens cap! JP :)