Have one, like it a lot, have sold it to my gf for her 30D because the corners are dark on my 1DIII (no, really

) The new version is apparently slightly better, but even the older one I have is quite nice. The biggy for me is that it's light and focus is pretty fast from the f/2.8. Focus is slower than the comparable Canon lens, but it's 1/3 the price and about 1/2 the weight... you decide.
The more I carry the 1D around the more I empathise with the guy I saw using a 28-80 on a 1DsII as a walk-about camera. His explanation was that it was cheaper than buying anything else... the lens was less than $50 second hand.
Moz