I have found, after purchasing a Nikon, that Canon's mid-range glass seems a lot more suited towards the advanced amateur. Nikon tends to either be more on the budget side or more on the expensive side, but there are few options in between.
However, from what I gather, Nikon's bodies tend to have a bit better build quality on the low end. Also, Nikon has a few budget lenses that are tack sharp, they are just slow and made of fairly cheap materials. This includes the 18-55 kit lens, which actually performs pretty well. But, if you want anything near f2.8, be prepared to spend a whole lot of money.
If I could start all over again and pick a platform to learn on, I think I would go the Canon route. Once I can afford high-end Nikon glass, I'm sure I'll sing a different tune, but for now I'm stuck with cheap and 3rd party lenses.