Leica cameras and lenses are pretty robust in construction. The ones I own are made with a lot of brass. I am not sure that there will actually be much of a weight savings over a DSLR and two zooms. The Leica kit is much more compact, however and easier to carry in a small bag. Others above in this thread have cracked the door open on some of the archania of Leica lenses. Simple story: Leica groups lenses in their line-up for marketing/naming purposes by the lenses' maximum aperture. More complex: the actual lens formulas have changed/been updated many times in the past 50 years. In my opinion, there are really no bad choices among these lenses and in my own kit there are lenses I bought used from reputable dealers (e.g. Tamarkin.com, Don Chatterton (now gone), KEH camera brokers) and ones I purchased new (B&H, Adorama). For a normal and longer lenses (like a 50mm Summicron, 90 Apo Asph), I don't see much advantage in image quality for the extra cost of purchasing new. For the newer wide-angle lenses (28/2 Summicron, 24/1.4 Summilux) it's more of a "get it if you can afford it" kind of thing. In my view, the advantages in image quality for these new wides are real and the lenses can, for the most part, only be purchased new (I have seen a few used 28's around recently, so this may be changing for that particular lens).
The newest generation of lenses have been called "clinically sharp" by some. These include the excellent 50/1.4 Asph, the 75/2, the 90 Apo Asph and the 35/2 Asph. "Asph" means aspherical -- now a computer-ground lens element that is not shaped like a classic "spherical" lens ("spherical" think: like a magnifying glass -- same curvature on each half of the lens). This innovation lets a lens designer use one piece of glass where two separate glass elements used to be required, but until relatively recently, aspheres had to be ground by hand, had a large number of rejects per batch, and were consequently very expensive compared to traditional lens designs. "Apo" is short for apochromatic and means, more or less, that the lens nominally focuses all wavelengths of visible light at the same plane. In terms of image sharpness this is generally a good thing, although a lens need not be apochromatic to perform well.
One final word of advice: If you are coming from DSLR world, the M9 will be a very different way of working, Senator, and it isn't for everyone. My free advice would be to get the camera and one lens to see how you like working with a rangefinder rather than a DSLR and then get other lenses as you get a sense of whether it is for you.
Best regards,
Ben Marks
