Here is what I have in terms of lenses/camera:
70-200 f/2.8 VR
18-200 f/3.5-5.6 VR
Nikon 50 f/1.8
I shoot a D200, and can see myself upgrading in the distant future, but I am not sure what to. I like a dx sensor because it helps get tighter shots in sports, but a full frame camera would also be baller.
The way I see it, I can go for a (more expensive) 24-70 and try to trade my 11-16 for a Tokina 12-24, which is supposed to have similar IQ, a broader range of focal lengths (I do sometimes feel limited by the 11-16), but also a stop slower. Alternatively, I can keep the 11-16 and get a 17-50/55, depending on brand. Either way, I would sell the 18-200 because keeping it wouldn't make any sense if I can cover those focal lengths with nicer glass.
I hesitate to stray from Nikon glass because generally, except for a few lenses out there, the Nikon really blows the others out of the water. I am still researching which third party lenses are decent in this range, but the Tamron 17-50 is supposed to be pretty decent, and is a lot cheaper. The Sigma and Tamron, on the other hand, dont seem to be quite so nice comparatively.
So NS, what would you do and why? Keep in mind that I do take my photography fairly seriously. I work on my college's newspaper and have also worked at a real newspaper doing photography for 2 summers.