I entirely concur with the review.
I have previously owned the F4 (with and without IS) and the 2.8 versions of this zoom and can say unequivocally that this lens is noticeably better in every regard, image-quality-wise, to those other zooms. Its one major drawback is the weight. You will notice it if carrying for any length of time.
Image-wise, it is IMO significantly
better then any
other lens in the same focal range with the possible exception of the 200 f2. So yes , it is better than the 135 that I had, except of course it is no where near as inconspicuous as the 135. The only portrait lens I have had that had a 'better' image quality was the 85 f1.2, where the bokeh is truly creamy and beautiful, but that lens only outdoes this one when fully open
and is only useful for static subjects
as the 1.2 lens' focussing is horribly slow, whereas the 2.8 zoom is fast and crisp, and has better IQ when stopped down than the 1.2 (which while contrasty doesn't have the same resolving power)
on this lens is phenomenal, I have perfectly sharp test images hand held at 1/4 second.
However, because of it's weight I never take it when landscape shooting (which is exclusively what I do nowadays) and because of its size and colour it's no good if you're trying to be inconspicuous.
For Indoor sports (like martial arts) and portraits and wedding type events is it far and away the best zoom lens there is for the ultimate IQ .
I bought mine purely for my daughter's wedding but due to it's weight haven't used it since, so if, like me, you no longer shoot weddings, portrait etc and have a bad back, I'd think twice about getting it. I'll be reluctantly selling mine just because if the weight, but I find it hard to let go of, as I've never had a zoom as sharp.
For landscapes, if you want this sort of resolving power, be prepared to cary some weight for the day. (although longer FL lenses are heavier still
So, for portraits, especially weddings, and sports this zoom cannot be matched.