If I had pots of money I suppose I would have both the 5D and the M8. However, the Leica is nearly £3,000 while the 5D is around £1500 (and without any of the problems experienced with the first batch of M8s). LL article suggests that the Leica is superb for B&W shooting but colour problems may not go away. £3000 for a B&W manual focus digital slr? And can anyone honestly tell me that a 5D with L lenses will not match the quality of digital images from an M8? I've used both the 30D and 1D Mark II which are both capable of producing stunning B&W shots with a little help from CS2, and in concert scenarios which are the most challenging for any camera (www.shakenstir.co.uk). In construction/engineering terms my gear goes through hell and back with no problems (and of course the 1D is fully weather-proof - within reason). Hell! for around £3000 you could pick up a mint used Canon 1DS MK II...
Depends on the L lenses, if it's wide lenses the M8 from what I've seen beats the Canon FF cameras by a huge margin (my 50mm f1.4 ain't great either). Not having AF is not a minus point, it wasn't left out by accident, I think they even left face recognition out as well. Comparing paper performance of the M8 against a SLR is pointless, you buy a SLR for what it does best, you buy a RF for what that does best. Making a list of what one has and the other doesn't have is missing the point.
A big plus for Leica is their quality control with the other big names you hear a lens can be good if you happen upon a good copy, Leica you expect bang on quality with any lens they make.
I don't use a RF, I use Canon FF in the shape of a 1DsmkII the best camera I have ever owned, but it does fall seriously short in a few areas. I can see the appeal of the "M" to photographers that need what the M8 does. The M8 should be regarded as a top class model, price wise it was never going to be cheap nor should it be. As for the quality of the files it produces they look top quality to me once you fit the filter, reminds me of my Makina 67, without a 1b filter the colours it produced were cold and drab, with it fitted it was rather good.
I also have as a backup camera a Kodak SLR/n, yesterday was the first job I've used it on for ages, I shot mostly on the Canon but did a few on the Kodak. The Kodak did the better job much to my dissapointment, on paper the Kodak is not in the same league as the Canon.
I have just turned from thinking I should sell it and get another Canon to thinking it does somethings better than the Canon.
I might even get a M8 for it's wide lenses after the dust has settled a bit more. Or a DZ.