I went from a D200 to a D7000, and never looked back. The D7100, that I now own, is built like a light, solid brick. The AF is very fast, the image quality is super.
I'm not the biggest fan of SD cards, but I LOVE the 2-card, backup option (plus others with he 2 cards).
Heavier does not always constitute better, and unless the larger buffer is really critical, I can't imagine not going to the D7100. It is the best DX available, from anyone, and should a D400 ever arrive (at what will be at least $1800.) you can always sell and shift...
The D7100 may not be in the exact mold as the D300s, but it decidedly replaces it.