I'm starting to yearn for some faster glass, and I'm thinking a faster long lens would serve me well. I'm happy with the current range I have (the 18-55mm kit lens plus the Nikkor 55-200mm VR), but the aperture on that 55-200mm is pathetically small. I find myself in dim light (weddings) or shooting outdoors in shadow (in the woods) or fast action (watersports), and f/4-5.6 just doesn't cut it. And I'm purely a hobbyist, so budget is a big concern. For that reason, the Sigma 70-200mm F2.8 EX DG HSM II caught my eye. Nearly all of the reviews I've read -- from the exhaustive writeup at DPReview.com to the individual 1-paragraph user reviews on Amazon and the like -- are quite positive. The general consensus seems to be that you get 80%-90% of the performance of the Nikon AF-S 70-200mm for 50% of the price (~$1600 for the Nikon, $800 for the Sigma). If that's true, I can definitely live with that. The one thing that gives me pause is the lack of image stabilization, since I've never used a 200mm lens without it -- but then I've never used a 200mm lens at f/2.8 either. I know some Sigmas (and Tamrons, etc) have questionable build quality, but all reports point to this particular one being built like a tank (DPReview concurs), although lacking some of the dust/weatherproofing seals that the Nikon has. I haven't seen hardly any discussion of this lens on these forums (it's only been available for 6 months or so), so I wanted to get opinions of anyone here who has used it. Sample images especially are great.