I have a Nikon D3300. Very happy with it, but I'm about to step up to the D7100 or possibly the Full Frame D810.
With that being said, I've quickly learned that the lens and the shooter are the most important factors for most quality shots. I shoot A LOT and that's the best way for me to learn.
I'll post up the D3300 for sale here soon.
What are the "step ups" with these models? It's hard enough to understand the differences between D3100, 3200, 3300, but then when you look at the 5000 and 7000 series, its hard for the untrained user to see the differences. Maybe they would be lost on a lightweight photographer?