Bought second hand from a store (with warranty.)
Good lens, sits most of the time on my camera (eos 350), but that's also because that's almost the only way to fit all my gear in the camera bag :-)
On crop camera's highly recommended if you want/have a 10-20 range lens if not, buy a lense in the, then more usefull, 17-55 range.
Build like a tank, although there is no weather seal.
USM quick & silent AF. Nice colors, bokeh & sharpness.
But remember: it's HUGE & heavy so when you point this lense (with the BIG hood) at someone he/she is going to notice it!