http://www.nikonchat.com/nikon-d5100-release/

Nikon D5100 or Sony NEX-5?
Which camera is a better overall? Should I wait for the NEX-7 to be released?
Well the proper SLR is always going to be better than the EVIL. The D5100 wins hands down.
The NEX-5 is really a camera for people who have a special requirement, that their system camera needs to be compact. Otherwise you have not advantage.
Nikon D5100: Unboxing