Minolta warns that the 1976-2008 50mm f/1 Noctilux is so fat that you'll cover the rangefinder window and have no focusing. Ditto for the 50mm f/0.95 ASPH (2009-) and possibly 50mm f/1.4.Minolta cautions not to use collapsible lenses or ultrawide lenses that poke into the camera body, but I've had no problems. My 1958 LEICA Super-Angulon 21mm f/4
works great, although it won't meter on the CLE, but it won't meter on any other LEICA either.
The only real gotcha is with earlier 35/1.4 Summilux-M and 35/2 Summicron-M lenses, each of which may have rear hardware that bangs into the CLE's rangefinder cam unless you do some surgery. No big deal, use the superior new LEICA 35mm f/2 ASPH
and 35mm f/1.4 ASPH
instead, and each works flawlessly, so long as you don't mind the 28mm frame lines.