I use my D300s and D200 with a two camera strap to take pictures of musicals. That way, I can cover 28-200mm at f/2.8 without switching lenses. But now my D200 is having shutter problems. Every 5 or 6 shots, the shutter will open but not close. If I wait a couple of seconds and press it again, it will close and produce a bad file for that shot, but it will then shoot a few more shots before it does it again.
So what to do?
1. Buy a used D200 for less than $300 2. Buy a used D300s for $850 3. Buy a D600 for $2100 4. Wait and buy a "D400" for $????
Well, the D200 is cheapest, but if I'm going to buy a camera, I'd like to upgrade, of course. And I'd like to get better low light performance. Rumor has it that the "D400" will have ISO 6400. That's only one stop more than the D300s. That's also true of the D600, but I'm sure the D600 will have lower noise pictures at ISO 6400. But if I get the D600, my favorite walk-around lens, the 18-200mm DX, which I use mostly when I'm not shooting musicals, means I'm in 10-megapixel crop mode. The D600 also means that I give up some of my telephoto.
Or maybe I should consider one of the other new cams, like the D7000...
So, what's the best low light Nikon camera right now?