[davidmanze]

Honestly ... I would go for the Sigma 500mm f/4.5 APO instead.

Faster, cheaper, better. So what's exactly the fuzz other than the Pentax tag ?

It doesn't really matter here but the border performance of the big P is downright poor ... and this a 7000$ lens.

I totally agree,the Sigma makes more sense although no WR..The "fuzz" is; that it does  represent a sort of commitment statement from Pentax that they're serious about their range of lenses and also Pentaxians don't have an awful lot to shout about in the way of new optics other than plastic fantastics and rebadged  Tamrons at increased prices. This to me was all about "prestige" for prestige's sake. 

     Personally, I cannot accurately  gauge it's sharpness from this review,but do you really think it's border quality is downright poor?

       Dave's clichés