Just got mine last night. I'm hoping to get outside with it tomorrow, but I'll have to brave some unpleasant fall weather - temps in the mid 20's with a 30-40 MPH wind. Still, it'll be worth it!
I picked this lens to complement my 70-200 II. Between the two of them, I should be well covered for most shooting situations. The 17-55 and 100-400 give me some extension beyond my good lenses, but at a cost of some IQ.