18mm sounds exciting, and surely is on my M6, but not quite as exciting on the M8, where it roughly corresponds to the traditional 24mm, So Leica is really just releasing lenses to cover the M8 crop factor with traditional and familiar FOV.
Leica make many much smaller lenses, but wide-angle lenses have always been larger, probably one of the reasons Leica did choose not to increase the aperture to something more sexy like 2.8, as this would also have hugely increased the physical size and weight of the lens.
This sweet little package comes with 8 lenses in 7 groups, it uses a 77mm filter and is weigh roughly 300 grams.
Personally for now I'm not too keen on additional viewfinders, and prefer to stick with lenses matching the build in frame lines in the M cameras.. Oh and I AM saving my money for "the" 28mm LUX which is way over due, as those of us who like shooting a 35 lux just don't get the same from a 28 2.8. Leica are you listening? We need a 28 lux.!
There is some competition, Zeiss have been selling a excellent 18mm f 4.0 for a while, and must have been filling in the market a bit. How these lenses stack up will be clear once shooters start making comparisons, for now Im guessing the Leica will have a edge. However only you can answer the real question, if that edge is worth a couple thousand dollars more?