I've only had the lens for a couple weeks, and while I do wish it had a bit more range, I've been very pleased. So far I've used it: snow-covered landscapes from mountaintops in Whistler, Canada; banquet and lecture halls with poor lighting, close-ups of family at home, and at my daughter's 13th birthday in a low-light ballroom dance studio. It performed quite well in all these difficult conditions. I rate it equal to my 70-200 2.8L in image quality, and it will be my primary lens for some time, I imagine.
No dust after a couple weeks. Mine is a used factory refurb copy, and I put a filter on the moment it came out of the box. Price-wise it was great -- from B&H for $850 with warranty and all, lens hood, and clear digital filter it was still $25 less than a brand new one.