Raid: I think you're going to love the M8. I bought mine new in early 2007, once all the quirks were known. I've never regretted it. The 1.3x crop never bothered me. I was a 50mm person with film cameras, so I simply started using a 35mm lens as my "normal." In fact, in some ways I like the slightly wider view of the 35mm lenses on the M8 than I do the standard 50mm view on film. I can still use my 50mm lenses, they have just become mild telephotos (or portrait lenses). Each lens retains its general personality, it just becomes one "notch" longer in magnification, and you lose the aberrations in the far corners.
Since you have a fair number of lenses, you'll probably be just fine. I would advise getting enough IR cut filters so that you don't have to change filters frequently while shooting (i.e. have a filter for each of your most-used lenses). The IR filters are very necessary to prevent the dreaded magenta cast. Even in B&W, pictures with the filters are sharper. There may be some advantage to shooting B&W filterless in low tungsten light. Once you have the filters, you simply forget about them and all's well. The only time they bother me is when shooting into a bright light source, where they can cause ghost reflections.
Focus is more critical than on film. Check your lenses wide-open focusing at infinty and at a meter or two. If a lens is consistently off, send it to DAG or Leica to be tweaked to M8 standards.
I use the original 35/1.4 Summilux ASPH (without the floating element). You may detect a slight rearward focus shift on some fast lenses as you stop down. This is an optical property of the lens design, not a lens defect. It usually happens starting at f/2.8, and by f/8 depth of field takes care of it. I just focus on the closest thing I want in focus between f/2.8 and 5.6, and/or tweak the focus a hard closer at those apertures. No big deal.
Sure, I'd love to have a sensor with the low-light ability of a D700 or K-5 in an M body. That may be coming at Photokina. But since that will probably cost $8K or more, it just isn't in the cards for me. The M8 actually does as well or better than film at ISO 640, and that's often enough with an f/1.4 lens. ISO 1250 is fine for B&W conversion if you expose properly. Meanwhile, you'll have all the conveniences of digital and rangefinder shooting.
You will want to code lenses of 28mm and shorter. A "Milich" or Voigtlander Type II adapter works well for screw-mount lenses. M-Mount lenses can sometimes be coded with a Sharpie marker pen and a "coder kit" template, or you can send it to DAG, and he will do it. 50mm lenses and longer don't need to be coded, unless you need the focal length to be in the EXIF. 35mm lenses are a toss-up. You will get very slightly cyan-shifted corners if you don't code them, but it's often not noticeable. CornerFix software or even a home-made gradient can solve the cyan shift without coding, but coding is far more convenient. Unlike the M9, the M8 does not have a way of manually entering the focal length in a menu.
Shoot RAW. The M8 (and M9) JPGs are not the best. I use Capture One. Some people prefer Lightroom. If you have a Mac, ask somebody else. 🙂 When you expose, bear in mind that the M8 has most of its latitude in the shadows, not the highlights.
If you were primarily or exclusively an "available dark" shooter, or mostly shot extreme wide-angle, the M8 wouldn't be right for you. But given what I know about you and your pictures, I think you'll be just fine.
--Peter