CPL filter

[digital]

I'm considering getting a Hoya 77mm CPL filter for my Sigma 10-20 on my Canon 60D.

Are there any gotchas with it? Vignetting, for example.

Is there a significant difference between the HD version and the Pro 1 version?

 

[Woodsy]

As for the difference between them, I've no idea.

Just be aware that the strength of the polarisation effect is dependent on angle of view and the direction you are facing with respect to the position of the sun. There shouldn't be any vignetting, even at 10mm.