8 out of 10 points and recommendedVery sharp, very quick autofocus, smallish, lightish, great out-of-focus blurA little long for really good handholdability
I shoot with a 6D, own several L lenses, including the very sharp 24-70 f2.8 Mkii, 70-200 f4 IS and the 135 f2.reviewed December 4th, 2014 (purchased for $688)
The 200mm is quite sharp at 2.8, I'd not hesitate to use it here, better at 3.5 and top notch through to f8. If you own the 24-105, you will really notice the step up in sharpness, but will miss the stabilisation.
A heads-up for prospective buyers: got to keep shutter speed up to maintain sharpness. I get some keepers at 1/250 but more at 1/500+. This means that hand-held, you'll be shooting at f2.8 and f3.5 quite often, perhaps at ISO 400 if you want smaller apertures, and probably during the day or in bright light. By the end of the day, you may find the ISO up around 800. When you get the shot, it's good! In a studio, on a tripod, this would be a brilliant portrait lens for shooting at, say, f4.5-5.6.
I bought this lens to travel with, and I think it'll be great for street scenes, but I'm wondering about dimly lit markets and temples in that I'll have to pump up the ISO and, of course, prefer not to. The 135mm f2 is terrific, hand-held, in dim temples but I wanted a little more reach.