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

What's better, the Nikon D90 or Nikon D5100?
I do not really care about the movie roles, as they hardly (if ever) use it. Me like the articulated LCD screen. However, the things that most concern are: the overall quality images, ease of use, ease of changing important settings to get the vaccine (exposure, white balance, etc), and for how long I can use the camera before you feel the need to upgrade. This will be my first SLR.
The D5100 is a D90 entry-level camera, so it is not as robust as the D90 The D7000 is updating the D90 The D90 will do the job for many years, five or six insurance
Nikon D5100 DSLR – Delivers Stunning Image Quality!