Any word on MTF ratings compared to the 70-200's? I used to own the 70-300 but sold it quickly because it was ok but just not sharp, especially in 300 range... I hope this is greatly improved... Also $1500?!? the 70-200 F4 IS is one of the sharpest lenses on the market (or at least canon's line up) and $300 cheaper... I could get a teleconverter for less $$ and perhaps get greater results...?
looking at the raw MTF's .. from 70-300 it's almost as good if not as good as the 70-200/4 L IS is from 70-200. I very much doubt that a 1.4 TC plus 70-200/4 is going to give you as good of results considering the 1.4 tc usually injects a pretty steep corner performance penalty.
at 300mm it compares quite well to the 300mm F/4 L prime.
and it kicks the consumer 70-300 to the curb as far as performance - MTF wise, fully weatherwise, full USM, updated IS, no rotating front element, etc,etc.
and it weighs in at nearly the same as the 70-200/4 + TC.
not sure what's not to love about this .. it's affordable (btw, if a semi pro can't afford a 1.5K USD lens .. there's a problem with the definition of 'semi pro') .. and MTF and physical wise, looks like a great lens.
the old 70-300 was a great bang for the buck - you put up with it's compromises because it was cheap.
anyone expecting a constant aperture lens .. I'm curious if they wouldn't have minded the double or triple price, greater weight and size that lens would have entailed as well.