Lets just rule out the D90 from the start. I am not arguing that it isn't a decent camera but it is getting long in the tooth and if you plan on having the camera a few more years, it is simply only going to get even longer in the tooth. This leaves the D5100 and the D7000. In terms of IQ, I doubt you notice any difference between the two cameras (though the edge would probably go to the D7000). The D7000 will have the motor in the body allowing the use of "older", non-AF-s lenses. Not really sure how big of a deal that is as the newer AF-S lenses tend to be better lenses anyway (if you already had a collection of non-AF-S lenses then it might mightier). The D7000 is much easier to operate. You have a dedicated dial for both the shutter and the aperture (the D5100 only has one dial); you can more quickly change just about any parameter on the D7000 more quickly: focusing (and you can lock your focus point), metering, ISO, just to name a few. And the D7000 uses dual card slots, something I can't live without! I use one for Raw and one for JPEG. You might use one for JPEG and one for video, or you might just use the other for immediate back up, or overflow. All of that said, if you are simply going to keep the camera in the "auto" mode, then I doubt the D7000 makes all that much sense over a D5100.