I'll be contrary as usual...
Canon Bob made a very good point: if you find yourself getting into photography seriously, then you're likely to stick with the same system you start with (because selling lenses, accessories etc in order to switch systems is expensive hassle).
But I don't think Bob went far enough. Handling the current Canon and Nikon bodies isn't that helpful, because in 5 years time they'll be obsolete but you'll still have the same system. And for heavens sake don't base your decision on whether the cheap Nikon lens is less plasticky than the cheap Canon lens!
I think you should look at the elements of Canon's and Nikon's systems other than the bodies, because there's more stability there. Here's my take on it.
* If you like photographing wildlife, birds, aircraft, and outdoorsy things - buy the Canon. They have much better options with regard to telephoto lenses, and are likely to continue to have for the foreseeable future.
* If you like photographing people and indoorsy things - buy the Nikon. Nikon's flash system is more intuitive and more flexible than Canon's.