For a super in depth and excellent review of the D40, check this one out. http://www.dpreview.com/reviews/nikond40/
Which Canon are you going with?
Unless you really need 10MP, a D40 is a better choice. Spend the money saved on something like the 55-200VR.
Nikon has better consumer bodies. Canon makes the best 'pro' lenses (other than specialty companies like Leica and Hasselblad) in the world. Based on your current camera choices, you don't seem to need 'pro gear' (which is really a myth, as anything used by a professional can be considered 'pro').
Also, you may want to consider Pentax if you're in to primes. Their FA limited series (31, 43, and 77mm) is usually considered the sharpest, smoothest (in terms of bokeh), most saturated primes on the market. Their new DA* f/2.8 SDM zooms, which will be out later this year, are very impressive. Besides their great glass, the K10D, a prosumer body, has weather and dust sealing, which can only be found in Canon and Nikon's $3000+ 'pro' models.
I decided to go with the Nikon D40 I did some research and tested the 2 cameras and i liked the grip and and the feel of the D40 better and the picture quality was better well atleast what i could see in the store
...I doubt any of us will be shooting in these conditions in the near future!plus no amount of weather sealing will save your camera from a sand storm or the the deserts of north africa/ middle east...
...I doubt any of us will be shooting in these conditions in the near future!