I'll suffer through even a terrible website if they have the coin I want. The coin is the key. Without nice coins, and without the type of inventory that I'm interested in, it doesn't really matter what bells and whistles you have on the website.
I agree with this Jason; however, I have one caveat. If the site is too painful to navigate, I'll give up the ghost trying to find a coin and I'll leave.
Very true. I was thinking the very same thing as I typed my earlier response. Another factor is coin scarcity, be it grade scarcity or true scarcity.