Depends on how bored I am, of wherther I want the features of a particular motherboard, or whether or not a vendor screws up and ships me the wrong board, for 1/2 it's normal price.
I'm an agnostic, P4, Athlon, as long as the code I need runs in the time I need it, I'm happy.
My P4 is now a server, and my main box is now an Athlon 2500 on a A7N8Xv2 Delux, but when the dust settles on the new Intel motherboards, and perhps the new socket, I may swing back the other way.
I rarely ever spend more then $100 on any part of a machine anymore. It's all fast enough, so it really comes down to where the bargins are.
Paul.