err... I guess it all depends on what your purpose is in getting the filter.
For me (newbie) it is just to protect my D70 kit lens. So I decide to just choose one that is around 10% of the cost of my lens, hoya HMC at $35. If too expensive filter, I have to buy another filter to protect the expensive filter.
next time if I get a 1k+ lens then I will buy a better filter.