I was seriously considering an M8 but put the decision on hold when all the "issues" surfaced (IR, colour balance, green blobs, 8-bit raw files etc). If Leica (or Zeiss, or CV, or Canon, or Nikon ...) ever come out with a full-frame RF-type camera (sans issues), I'll be sorely tempted. I have had a Canon G5 and G7 (both since sold) and now a G9.
Comparing the handling of the G9 with my Leica M7, I prefer the Leica, but the G9 does handle extremely well for a digicam. Also the G7 and G9 have a more pocketable shape than the earlier Gx's.
After about one month of use, I dropped my new G9 from shoulder height on to a hard pavement. It was bitterly cold (in the UK) and I tried to remove my glove in a hurry to get to my cellphone. The G9 was on a wrist strap and it came off with the glove. There is a small ding near the ISO dial, and the rear plate is slightly buckled at the top-left corner. Adjusting the diopter now requires a finger-nail rather than just rolling it with a finger. Otherwise the camera seems unharmed. Focus is still reliable. Maybe I was lucky, but it has increased my respect for the G9 considerably.
In good light / low ISOs there is little difference in IQ between the G9 and my CAnon 5D. The slight difference there is is probably due to color gamut. I have the 5D set to Adobe RGB which is not available on the G9. The 5D can be used up to ISO 400 with virtually no noticeable loss of IQ, and up to the maximum of 3200 with careful exposure and a dose of Noise Ninja. The maximum on the G9 is 1600 ISO which really needs Noise Ninja (or similar) and can only be considered satisfactory for small prints, so you can't see the softness caused by the NR. I would imagine the M8 is somewhere between these two cameras in this respect.
The worst thing about the G9, IMHO, is the viewfinder, which (like the G7) only shows about 70% of the image, and this varies slightly with focal length. It is pretty close to accurate along the bottom edge, but cuts off the image by 10-15% at the top and each side. Knowing this, I still use the viewfinder, composing tight along the top and sides, and cropping the final print in the computer as may be necessary.
Others have commented on the DOF issue in that it's virtually impossible to throw the background OOF with the tiny sensor. AFAIK, there's no really satisfactory way around this. Edit: even with the lens wide open the DOF is still *much* deeper than it would be with the same FOV on a 35mm / full frame camera.
Just my R$0,02 ...
Edit: Addendum - several months later, my G9 has started to misbehave - the optical zoom viewfinder stil zooms out OK, but it won't zoom back again until you turn the camera off (then on again). I'm pretty sure this is a delayed readtion to the fall it sustained as described above. Oh, well ... I wonder if (1) it can be fixed or (2) I can live with it, or (3) I'll get another ...