I had a similar dilemma coming from my d50. I chose the d5100 and two afs kit lenses. Head and shoulders above my d50 for af speed and accuracy as well as I think the d5100 is even easier to use, eve using the menu to change a few settings.
I'm sure the d7000 would be evn better with he larger viewfinder, but it's a compromise. I have to say I've already had the articulating screen be very useful grabbing a few shots above the crowds heads at spot events that I'd never have otherwise gotten. Honestly I don't think the small viewfinder is all that bad... Smaller yes but still very usable.
I threw a $20 third party grip on it and it way easier to get a grip on now and just feels more substantial with my afs 80-200 2.8 on board... With the added plus of taking it off and using a small light lens when I want to be portable and lightweight.
Auto ISO is one of my other favorites. Set the max and minimum ISO and use M mode to get whatever dof and shutter combo I want without worrying at all about having to mess with ISO to get the right exposure. Couldn't do that with my d50 unless I just didn't realize how . And with such good ISO Performance I dont even worry about maxing out at 6400 either.
Very happy with the d5100 and don't regret not choosing the 7000 at all, even for the action/sports stuff I do a lot of at kids sporting events. A vast improvement over my d50.