I've not been serious about photography very long and started of using cheap filters from Hong Kong via a well known auction site, needless to say they were cheap and not very effective.
This along with upgrading to Canon L lens prompted me to seek filters that warrant being placed on any lens, I ordered the Hoya HD Polariser and was thrilled with the quality when it arrived, superior fingerprint repellent,easy clean glass,smooth rotating wheel make this by far the best filter I've used.
It allows for (I believe) 25% more light transmission that the competing Polarisers out there including the Pro 1 series, I also own a £95 B+W polariser B+W 77mm Circular Polariser Filter With Multi Resistant Coating
but this HD one knocks spots of it (IMO),I wish I had waited for the Hoya HD to come in stock before I rushed into buying the B+W..............comparing the Hoya to the B+W you can understand why it allows more light transmission, the B+W looks more like a Neutral Density and gives noticeably slower shutter speeds than the Hoya HD
Like I said I've not been serious about photography for long but recognise these Hoya HD filters as a quality edition to anyone's kit.
You won't be disappointed,I'll be sticking to these in the future.
**Update** April 2010
I feel I was a little unfair and nieve about the B&W, Yes, its darker glass and results in slower shutter speeds and yes the glass is less figerprint repellent than the Hoya HD but one thing the darker glass of the B&W gives you is a deeper blue sky and more pronounced clouds.#
that not taking away anything I've said about the Hoya HD range , because it is a quality range of filters, including the clear protectors which are just as impressive.