Asking for input from anybody who has used Canon's new EF
70-200mm f4 L IS lens with a circular polorizer on a 30D DSLR.

    My concern is how well dose this combination focus, does the
addition of the C-PL slow down or make focusing less accurate?  After
all in theory a C-PL would add about 1.3 stops making it have to focus
@ an effective f6.3.

    I'd much rather the new 70-200 f4 L IS over the 70-200 f2.8 L
IS mainly because of the reduced size & weight since it's likely to be
used hand-held 90+ % of time.  Anybody with the non IS version who
also uses a C-PL can probably answer this question as well because I
would expect very little difference between the 2 in this regard.

    Don't want to spend about $1,250 US on this new lens only to
find that it does not focus reliably with my 30D with a C-PL on it.
If it's going to be a problem with the f4, would the f2.8 version be a
better choice if I can tolerated the added size & weight (1.7 Lbs. /
3.2 Lbs.)?

    Thanks in advance to all who might respond

    Respectfully,  DHB
     

"To announce that there must be no criticism of the President,
or that we are to stand by the President, right or wrong,
is not only unpatriotic and servile, but is morally treasonable
to the American public."--Theodore Roosevelt, May 7, 1918