...own XH-A1 and will be working on river film and want to get a polarizer but so many brands. Which is best? Also would like opinions on best shotgun mic for 200-300$ range with XLR...any opinions? Thanks

I'm totally happy with my B+W multicoated circular rotating slim polarizer (it's a 77mm used on EX3 and 7D) but I think it's well under your budget - there might be better options. I'd use the money you save and put it towards a Rode NTG-3 which I'm equally pleased with too.

I was going to ask if you actually need a circular polarizer at all but I remembered it came up before: http://www.dvinfo.net/forum/canon-xh-series-hdv-camcorders/134892-linear-circular-polarizer-xh-a1.html
If I might be so bold, may I suggest that we pay particular attenton to posts no 12 and 15 on this thread as they address fundamental issues about the understanding of the word "circular?"

I started off years ago with a CP like Andys but never use it now on the A1, I found you have to take the lens hood off to adjust it or you risk getting finger prints on the filter. IMO you can get more controlled 'polarizor fx' in post.

I find a much more useful filter on the A1 is the B+W graduated filter which allows more detail on the lower half, ie: the ground .. or in my case under the wings of aircraft.

FWIW, yesterday we were shooting an airshow. The sunlight here is brighter than the northern hemisphere and the sky was a bright light overcast, like a giant scrim which I like for airshows. I needed an extra ND filter on the lens .. I've got the B+W 501 (1 stop) and 502 (2 stops) and find the 502 is more useful on the A1. If you do a search there are good prices, watch out for knock offs.

Yep the NTG-3, without doubt a great mic.

Cheers.