I had an M8 which I recently sold. The camera did have a lot of problems -- many of which have been resolved. But compared to modern DSLRs, it was just too much trouble, and for most people I think the same would be true of the M9, especially for landscape. The biggest problem is that there is often difficulty in achieving critical focus -- the rangefinder mechanism is an old-fashioned system, good in its day, but I think it will always have trouble working with high-resolution digital sensors. You will always have a higher percentage of missed shots than with a DSLR. You also have to understand that these mechanical systems, and the lenses, will "drift" -- and then have to be sent away for an expensive recalibration. Also, it is sometimes impossible to have all your lenses focusing perfectly at the same time. I had the last-generation f1.0 Noctilux, and could never get it to work exactly right with the rangefinder mechanism. I'd focus, and then I'd have to give it just a tich more turn...I'd have to turn it until the rangefinder just started going out of focus and then it would usually be in-focus....but that's no way to go through life. (There's no live view, so you can't use that to focus.) The M8 also has an inadequate infra-red filter, and so you are required to use IR/UV cut filters on the front of the lens to keep the color balanced...and you still get color artifacts. That was just one of the big problems with the M8, which went away (mostly) with the M9, as I understand it. When everything was in-sync, the M8 was just fine, but I really don't think it is much of a match for more modern DSLRs.
If I were in your shoes, I'd go for a compact DSLR like a Pentax K5, and then a few primes in your most-used range. That would keep the weight down quite a bit. And the thing with a DSLR is, you use both hands to hold it. With a Leica, you basically hold it in one hand, and focus with the other. If you have a hand problem, you might find a Leica is more difficult to use than a DSLR. Before making your move, you really ought to try a Leica. No may no Leica. 8-)