Oops, was typing my last response as you popped in! Thanks a lot for the recommendation. I was a little torn between the Sigma and the Tamron but glad I chose the Sigma.
Glad your happy with it - looks like it takes some really great photos. I ended up selling off my Nikkor 70-300 mm AF-S G, It just wasn't getting any use after I got the 200 mm and a 2x teleconverter. It's a great combo, I've got 70-200 mm at F/2.8 and if I add the teleconverter 140-400mm at f/5.6.
I've been giving some serious thought to the Tamron 150-600 mm once it's released in the Nikon mount. I just haven't decided yet if the extra 200 mm reach would really be worth the cost. Going to have to mull that one over for a while I think.. lol. But for now I'm looking for something in a wide angle zoom so it will most likely be either be the Tamron 17-50 VC 2.8 or the Sigma 17-50 OS 2.8. Need to research them both, the Sigma is a little more expensive but I've had such great luck with my other Sigma that's kind of the direction I'm leaning in at the moment. I'm planning on hitting some car shows and such this summer and I need something a little wider than the 50 mm prime.