Originally posted by Rude The amount of good used glass available for Nikon under $500. Pro AF glass has gone through multiple renditions, so you can get a 3 or 4 generation back zoom lens (like a 35-70 f/2.8 or a 80-200 f/2.8) or primes like 85 f/1.8; 180 f/2.8; 50 f/whatever; and any wide angles. Even 3rd-Party offerings are less expensive, since they have so much more competition.
This is a point that so many Pentaxians try to make a positive for Pentax, yet I have found very untrue, at least in the US.
There is a lot more used Nikon glass available than there is Pentax glass. And if you want AF, it's not even close. Plus, with the D700 and other upper-end bodies, the compatibilities increase.
BTW, I had a 80-200mm f/2.8 and it was an absolutely killer piece of glass. I even had the pre-AFS version, and I loved it. I hear the AFS one is even better.