The D7000 has Built In Auto Focus Motor while on lens mount they have nothing different as the Old lens cannot go for Autofocus if mounted on the D5100, as it depends upon CPU Power Auto Focus Lenses which are bit costly while other old ones are Cheap, also many other Brands are tested with D7000 and in Noise its Super in Image Quality.
Still in Islamabad cannot find the Body only deal as its on 125k with 18-105/w Lens Kit but i am not interested in that lens at all. Also need to build the cash more as i am more inclined toward the D7000 as i will go for the future equipment for shoot out as the camera gonna stay with me for some time. :B
Another big thing is the battery life of the D7000 its almost double to D5100 and Auto Focus points which are double, while Weather Proof and Magnesium Alloy is added benefit like the Semi Pro or Pro Cams.
I am looking for more and better suggestions as i am yet open to purchase while i think currently many users are looking for the D7000 upgrade or the purchasing and confused in between D5100 and D7000.
Certainly thats a big thing to think about as the DSLR World without Lens addition is Mess and ends up in Frustration as Lens Cost can be even same or double at the end of Maths