This is the 1st Canon lens I am completely satisfied with. I have/had 35mm/1.4, 50mm/1.4, 85mm/1.8, 135mm/2, and tried 16-35, 24-70, and some Tamaron lens, but this is "D" most impressive one. I am newbie in lens, and I am picky about lens with too high expectation usually in terms of sharpness.
I had bad expeience with 16-35 and 24-70, though just because of this 70-200ISlens, I am willing to try one more copy on those lenses before I buy a Sigma or Tamaron one.
For price, I like it lower too, but I know this lens' performance matching its price.