MY local photo shop claims that B+W's standard circular polarizor is quite sufficient for use in Vancouver and that the MRC version is not neccessary. Any opinions on this?
Also is the F-Pro slim enough for use with a 17-40L?
First of all, the MRC designation means that the filter is multicoated. That means it is FAR less prone to flare. This is information that has been well known since multicoating first came out in the early-1970s. Serious photographers only use multicoated filters (and lenses). Do not be persuaded by this dealer who is misinformed. Frankly, if he told me that (and knowing what I know) I would not only walk away, I would advise others that he giving bad advice.
Secondly, you don't need a thin mount filter (polarizing or otherwise) for the 17-40 if you are using it with a 1.6x reduced sensor size camera (D30, D60, 10D, 300D, 350D, 20D). If you are using it with a film body or a 1D or 1DS, you need the thin filter mount with this lens.