No surprises in this department, Nikon has always left out the focusing motor from entry level bodies to distinguish them from the non-entry level bodies. Depending on what lenses you will use, that may or may not affect you. Naturally, if you want to use excellent AF-D lenses like the 50/1.8D, 50/1.4D and others, you will be tempted to choose a "better" body like the D7000.
For existing Nikon users, it may take some time to get used to the button shifting.
Caution to serious amateurs when buying entry level Nikon bodies (not saying entry level bodies are crap, but these are some things you should take note of, but seldom mentioned in reviews and stuff), from my own experience
-If you wish to use cheap (and not to mention better built) old AF-D lenses, entry level bodies aren't the best choice. You may think you can just manual focus with the 50 prime or something, but it's not optimal.
-Entry level Nikon bodies do not support flash high speed sync. I do not know about the D5100, but if they don't change anything, it won't have high speed sync which is very useful for outdoor fill flash especially when using large apertures.
-If you want to use manual mode a lot, it is not impossible, but with 1 dial, you'll take much longer to adjust your aperture. Most of the time, you don't have to shoot manual, but when you don't, 2 dials allow you to set one to ISO, so you don't have to press a button to change ISO
-Entry level Nikon bodies do not come with an ISO button. You can program your function button (which is also the button to trigger timer mode), but you lose the timer mode button. Not a big deal for me since I seldom use the timer.
-Entry level Nikon bodies do not support battery grips (I do not know if the D5100 supports battery grips). If you plan to buy heavy lenses, they may not balance properly on the bodies. You can go for third party grips, but bear in mind they they need a not-so-fancy GPS cable if you want to use the vertical grip's shutter release (not a big issue if you don't mind third party stuff, and if you don't mind not having the vertical shutter release)
You can choose not to swivel the screen what, it's still a model that lies between the D3100 and D7000. I have no doubt that it will produce great photos, in fact, seeing that it is using the D7000 sensor. But I have doubts regarding the controls of the camera.