Get a d800 and be done with it. You get a great FX & DX all in one.
I could, but I can't justify it to myself. It isn't cost as much as what I want. I'm not a pro, no desire to be. I'm spoiled by the D300. Went and played with a D7000 again today to try to talk myself into the D7100. It just isn't a pro-level body from a controls perspective.
The mirrorless capabilities, especially in m4/3'rds, is getting so good. What is sad is that the micro 4/3'rds has as good or better lens choices than DX (right now there are 54 lens choices available on B&H, 22 of which are faster than f/2.8). For instance, at the same price as a D7100 with the kit lens you could get the Olympus OM-D with a 12-50mm (24-100mm in 35mm format).
Sad to say, but IMHO, Nikon is doing a terrible job meeting the needs of the advanced hobbyists/amateurs. I have, and enjoy, the Nikon 1 V1 as a second camera. It and the rest of the 1 series are good but not great. The rumored DX mirrorless might resolve this, but right now Sony and m4/3'rds are clearly superior.
The D7100 appears to fit in that same mold: good, maybe even very good, but not great. Fortunately for me and unfortunately for Nikon, the D300/D300s is a great camera which created high expectations in a successor. Maybe the rumors regarding Canon's roadmap may pressure Nikon to release what folks have called a "D400". I hope so. But for now, I think I'll wait to see if Nikon shows anymore DX love this summer. If not, I'll probably jump into the mirrorless world.