I used to buy the "reasonably priced" polarizer until I got my L glass. Part of the problem I had in the past was that I had lenses various diameter. (52mm, 58mm, 67mm). All my L glass has 77mm thread so it's easier to buy nicer filters (Now I've only got high end Hoya and B&W) one of these days I'm going to finally put out for the Lee 100mm filters, but not likely anytime soon.
If your goal is to protect, save your money and use a hood. If your goal is image quality, spend as much money as you possibly can (on Hoya, B&W, or Lee) I've also heard good things about Singh-Ray, but never tried them.