With a standard PL you might want to overexpose by 1 or 2 to compensate for the filter. I am not sure but it sounds like it might work

As for a cirular PL I think that might be a big difference seeing as how you can rotate it to have max PL or no PL or in between. I am going to look into getting one for my camera next.

That link is awesome with a lot of good info. A couple of more that I am on is:

http://photography-on-the.net/forum/
http://www.phototakers.com/forum/
http://www.photographycorner.com/

Each one has some good things to offer but are not as indepth as the first one I posted.