And you say that because you have taken potos with a 3100 and a 7100? I´ve been shooting for maybe one year and a half (with a 3100), and I feel I already need better IQ. I do print a lot and I really want the best I can get. For all who shoot with a 3100, I´m not saying it´s a bad camera, but it´s not fast, the focus isn´t always dead-on (improved a lot since I got a 28-85 though) and the mediocre low-light sensitivity drives me crazy... Again, I´ve only been doing this for two days, but it´s not enough for me anymore... BTW, I will be trying to get some opinions about an upgrade.
So I have been shooting both for quite some time. I've also shot the D7100 since it was released. I have been a pixel chaser since the early days of digital and I felt just like you. However, the longer I have been shooting the more I realize that all these extra megapixels do is put more money into Nikon's pocket.
The fact is, for photos on the internet or prints up to 11 X 14" you will be hard pressed to see the difference between 6 Mp and 24 Mp. The real difference will start to be apparent at 16 X 20" and larger. Even given this, technique, exposure, and lens choice will make a greater difference to the results than how many Mp your sensor has.
Try it for yourself. Take an identical shot with your D3100 and your D7100. Use a tripod, the same lens and the same exposure. Then print both at 11 X 14" and show them around to friends and neighbors. See If they can tell you the difference.
Regardless, enjoy your D7100, it is a beautiful camera.
