My assessment from a lot of looking around, trying things, and talking to lots of other people is this (in an extreme over-simplification):
- If you want point-and-shoot, go Canon. They are hard to beat across the entire range, both in terms of features and image quality.
- If you want a DSLR as a hobbiest or serious amateur so you can do things that even the high end point-and-shoot stuff won't do, go Nikon. The features and image quality, particularly on the upper end of the non-professional line, is hard to beat. I've had more than a couple Canon shooters look at my D7000 and D600 with envy.
- If you are young and have aspirations of perhaps making photography a career, take a long hard look at Canon as they seem to own that space, so any investment you make now in Nikon or any other brand will either need to be shelved or sold off at some point to make the switch. Good glass is expensive and a worthwhile investment no matter what your level, but it's easier to hang with what you know than to have to change over down the road. And if you're lucky enough where someone will hire you and let you shoot with company gear, it's nice to be able to use the same stuff you have at home.
Most of us here find ourselves in the middle group, though there are indeed some who shoot professionally and do so with the same gear I've mentioned in that section, so there's plenty of support for that part of the Nikon line. One thing not to neglect is what your friends and family shoot. The ability to trade, share and borrow gear is a nice benefit. My brother is a Canon pro, and I thought long and hard about that before buying my D7000. In the 2 years since I've heard more than a couple verses of, "I just sold my XYZ lens. You could have gotten a deal on it if it would have fit on that camera of yours." But I also heard him rave about my D600 when he played with that over Christmas.
I think you'll find a way to be happy with either choice - and a way to regret not going the other way on occasions. If you go with a Nikon then you've already found a good group of people to push you through the learning curve.