Pros: easy to use, does a lot
I owned a Nikon D40 several years ago and loved it. Unfortunately I need some money so I got rid of it. Since I missed photography so much I did a bunch of research on a camera. I am not very experienced although I did do a lot of work with my D40 and took a couple photography classes so I was looking for something versatile yet easy to use. This camera definitely did the trick. I can't really complain too much I just wish that the display did what the D5100 did (the swiveling out). Other than that it's a great camera.
My favorite thing about the D3100 in comparison to the D40 is that it takes videos. The videos are awesome quality as are the pictures. I love that you can use live view so that you don't always have to look through the viewfinder to take pictures. It would have been nice if the package came with a memory card, but I guess I can't complain about that. Overall this is a great camera for people who love photography as a hobby -- what stopped me from paying the extra hundred dollars or so for the 5100 is that I am not a professional and do not need most of the features it comes with.