[Jamie Roberts]

Hmmm.... just to clear a few things up with my experience...cause I did (and do) a lot of shooting with R glass on Canon bodies still...

• Yes, you have to manually focus the R lenses on a Canon body
• The results look entirely differently than the Canon glass. Really. Contrast, colour distortion and CA are all obvious and really telling improvements using Leica R glass (old and new) instead of Canon glass. Try putting a 30 year old Summicron 50 on your 5d and compare it with the 50 1.8 Canon (or the 50 1.4 for that matter). Hah! Or shoot a high-contrast subject "into the light" and see what your EOS sensor is actually capable of recording
• Focus-confirming adapters actually blink "O" when focus is obtained, just like the AF lenses do. You're still manually focusing though.
• M metering in the newest 1 series mark 2s and probably 3s, and with the 5d, works exactly as it does with EOS lenses, without any compensation or resetting of the meter, etc...
  
  No, shutter priority (Tv) does not work, since only you can change the aperture ring
• I'm sure Robert S. is correct about the Canon 1d needing to be set to 1.0, and I don't use Av that much.
  
  But--and this is a big but--it seems to me that my 5d Av is just about as accurate as it always is when using Leica glass--the meter, after all, is reading Through The Lens, not through the "computer" in the lens. Remember, light varies even if the aperture doesn't
  
  So with any modern EOS it doesn't matter what the EXIF information says in the slightest, and that includes the Rebels.
  
  The camera reads the light entering the stopped down aperture on the Leica lens, and adjusts shutter accordingly (and usually wrongly, just it the autopilot does with EOS lenses Which is why I shoot M most of the time anyway!
  
  Anyway, the metering works exactly the same for both confirming adapters (that fool the electronics) and non-confirming adapters.