Nikon is fast closing the sensor gap - the new D200/ D80 offerings have pretty much eliminated the old noise problem, and both of these cameras will push Canon to do better.
In terms of glass, both systems have soem excellent lenses. It is perhaps a bit harder to tell which are the good Nikon lenses - except perhaps by price - but IMO they cost more for same - just look at what their macro lens costs - the 100mm one ( or is it 105, all these noink products look the same to me...
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I really don't think it matters which system you use. i use Canon because I always have. there was nothing rational in going with a n Eos DSLR - even all the consumer glass I brought over from my film Eos has been upgraded and replaced ( thanks to POTN!) so the old excuse of compatibility with your lens collection , in retrospect, was pointless.
But I have no regrets at all. Canon all the way!