Sorry, this is a bit long...
I had a chance to spend a little time with the SL.
It is not as big as you think...it's bigger than an A7 and smaller then a S2. I found it to be comfortable to hold. Please note, I have really big hands. Focusing was very quick with the "kit" lens and the viewfinder was fantastic. It handled very nicely with a Summilux 35 and it was built like a tank.
However, I don't think specs (which are pretty good) or any of that is really what this camera is about.
Forgetting the brand and forgetting the price, having a full frame mirrorless camera that is optimized to use nearly all of Leica's legacy glass and newly developed glass developed just for this system is what makes this camera unique and relevant.
I think the real problem here is Leica's marketing. The whole "PRO" thing and really playing up the fact that it's mirrorless is sort of like putting a big "TURBO" or "RACING" sticker on your new Audi. Mirrorless is not a new technology and it’s not that exciting to hear “PRO”. Nikon and Canon do well with the pro market and they can support it.
I believe that this is a camera that would appeal to many artists, enthusiasts and yes, even some pros.
However, I think the photographer who will really be interested in the SL includes, but is not limited to...
Those who appreciate a full frame camera that can accept a collection of Leica glass.
Those who want something different than Canon or Nikon but with an equally durable and perhaps a more expensive feel.
Those who enjoy the Leica mystique but don't like rangefinders or manual focus.
Of course there are, and will be many others...
I understand that many (most) people don't "get" what Leica is all about. I can't blame them. On paper, Leica will generally loose a battle of “tech specs”. Not to say that the cameras aren’t great, I think they are. The fact is, the lenses are some of the best (cue Clarkson) “…In the world”. However, that being said, I think those who are Leica fans may be more sentimental / emotional with their camera purchases. They are looking for the experience. Whatever that may be. Using a rangefinder, seeing that “Leica glow”, whatever. And, truth be told, some may just want the "best". Sometimes, the best just = expensive.
I applaud Leica for taking some risks and for trying to do different things for their user base. I don’t blame them for trying to expand their reach with cameras like the T and X series. Ultimately, they don’t usually play well in the same sandbox as the other kids. They are just too pricey and don’t have the latest in technology.
In the end, I don’t think that this camera is intended to compete with Nikon, Canon, Sony or any other camera in any other market.
It is for those who are in the market for a…Leica.
Just my .02 which is worth .00