I own 2 M8's, tested the M9 3 times, printed files from both, and concluded the M9 was not that much better than the M8 when i looked at prints 17"x22" from my Epson 3800 on Exhibition Fiber. I bought my first M8 later in 2007 well into the production run and my second on Ebay afer I tested the m9 3 times. My conclusion is when used right, the M8 is a great tool for digital rangefinder photography. In fact, maybe the best camera I have ever owned. I say this after being involved with photography since 1987, darkroom for many years, Leica M4-2, M6, Fuji GSW 690, etc,,, the quality is outstanding (keep ISO at 640 and below) and most importantly, the productivity (digital workflow) is enhanced beyond my greatest expectations.
My second M8 was an Ebay item for $2000 and is in mint condition with no issues AT ALL! That is my backup in case my well used one ever goes to Leica for any repair.
By not buying an M9 I freed my resources to purchase lenses which today are worth much more than I paid originally. In fact, if I had a choice between an M9 with few lenses or an M8 with many lenses for the same money, I would take the M8 with many lenses.
The M8 can produce some noisy photos, even at ISO 640 in low light (shadow areas?) , but the miracles of post processing (I currently use CS4, layering, and selective noise reduction. What amazes me is how much you can pull out of an M8 file and work with. Another point: When you up-size the M8 files, especially at the lower ISO's and with lenses like a 50mm Summicron in studio conditions, the files are almost the same as what I would get out of an M9 or any other pro DSLR with high megapixels!