The D7100 looks great on paper. I'm eager to see the results of field and bench tests. Like many film shooters, I held out on going digital as long as I could. The D200 was my first DSLR. I later moved to the D300 (still an excellent workhorse camera) and then the D7000, mostly for the better low-light performance and video capability.
While I'm pleased with the D7000, I miss the slightly larger body of the D300. It just seemed to fit my hand more naturally. It looks like the D7100 is a bit larger than the 7000, so it might be a better fit for me. As an HDR shooter, I also miss the 9 exposure bracketing range of the D300. The D7000 limits me to a three exposure sequence.
One thing that really annoys me is the need for a new battery grip with each new camera generation, as well as a new set of RRS L-brackets. These ancillary items are really pricey and I'd instead prefer to spend money on quality glass and lighting gear.
I'm holding back on buying the D7100 for now and will continue to hope for D400 within the next 12-14 months. Perhaps I'll be able to use the grip, batteries and brackets from my D300, but somehow I doubt I'll be able to.
One thing I'm sure of is that I'll stay with the DX format at least until 2015. I've been more than satisfied with DX and I currently have a nice assortment of pro DX lenses. I'd like to see Nikon introduce a couple of fast wide-angle primes. A 12mm f/1.8 and a 20mm f/1.8 would really round out my kit.
Right now, however, I'm investing in upgrading my computer, software, monitor and printer, so any new camera purchase will have to wait until next year.