Without doubt, the Canon EF 135mm F2L lens is one of the best autofocus lenses ever made. The colour, contrast, sharpness and bokeh on this lens is out of this world. I wish I had more chance to use it, but it's too long to use indoors, especially when mated to a 1.6x crop camera, like the Canon 10D that I use.
I had this lens too. AMAZING autofocus. Very fast, very quiet and spot on. First time I used it, I thought the lens was broken because it autofocused so silently. I had it set on AI servio, and couldnt believe that it was really focusing that fast.