I was in a dealer the other day, and the salesman was expounding
upon how great the newer 70-200AF-S was in terms of focus speed
over my 80-200/2.8 AF-S, which I have always thought was
stunningly good in that category.

Since I seemed doubtful, and no doubt he wanted me to upgrade,
he mounted one on a D200 body for me to try it out.  I have to
say, I was decidedly unimpressed.  It could be that the D200 has
focus problems (which I highly doubt), or it could be that it
just isn't true.  It seemed to me that the 70-200 did focus
well, but it seemed to 'glide' into focus, whereas the 80-200
snaps instantly there.  It does make more noise, as it seems to
jump into position, whereas the 70-200 seems to be smoother, but
at the price of being slower.

I'm curious what others that have used both think about this, I
was definitely not seriously tempted to upgrade based upon that
brief testing.  The dealer didn't like my response, to which he
gave up the time-abhorred answer of "Well, the pros don't agree
with you".