I tried a D7000, after using a D300s for quite a while, and did not like it. It was a combination of the size and layout, but also the lack of features and performance.
I now have a D7100 and have disposed of the D300s. There is no downside trade-off in the performance and features of D7100, and you gain a significant number of MP, as well as much enhanced dynamic range.
You also gain far more up-to-date firmware, with better in-camera noise control, better hight ISO performance and Nikon lens auto distortion correction (if you shoot JPG or use a Nikon raw converter software).
You do not get a dedicated AF-On button on the back, but can program the AE-L/AF-L button to perform that function. You don't get the 2 banks of up to 4 custom settings, but do get 2 user modes to program. You do not have a 10 pin cable connector, but rather the remote plugs into the side of the camera. And there is no built-in PC Sync connection, an AS-15 is needed to do that.
The items in the above paragraph were a fair trade off for me for the enhanced performance. (I also have a D3s and D800e if I really need that stuff for some reason.)
As for size, it is definitely smaller and lighter. You may find that good or bad. I find it great for traveling lighter and for casual shooting. My hands are not particularly big, so that isn't an issue.
I will likely never use some of the "consumer" features of the D7100, such as the scene modes. But for $1,200, it is a great value. (Heck, I've never used the video mode of my other 2 cameras, except by mistake!)
I was waiting for the "D400", but considering my other 2 camera bodies, decided that I really didn't need to wait for the hoped for features of that once the D7100 was released. With the great DR, it is a D800 lite.