Customers most agreed on the following attributes:
I primarily use this filter to product the lens,which it does quite well.
I like a perfectly clear filter to protect my lens. This one is very high quality and made for durability.
I dropped my camera and the protective filter shattered - probably due to side impact on the filter rather than a direct hit to the glass surface. So, this HOYA filter is the replacement. It looks to be high quality and should do the job well.
Main message is, get this filter or something similar to protect your lens!
The Hoya Pro1 filter is excellent quality and construction. It is somewhat on the pricy side but you get exactly what you pay for. I will be purchasing additional filters, such as a circular polarizer, and rest assured they will be Hoya.