Seriously though Darren, although I personally use Canon, it's because I was put onto the brand by our magazine's photohrapher who has used both brands and is now a died in the wool Canon user.
But from what I hear, both brands are pretty much equally excellent. The pros tell me Canon has offered better after-sales service in the past (although $50 for a sensor clean isn't what I would call good after sales service!), but I also hear they have 'restructured' (i.e. significantly downsized!) at Canon North Ryde recently so that it remains to be seen if the service will continue! Canon is also said to produce better lenses, but they haven't released a new L series lens for many years (in my price range anyway!), so I'm sure Nikon has done some catching up.
As Grahame said, I hear the new Nikon D300 is awesome, and I've seen some fantastic results from the D300 from members of this board.
I suggest you establish what features you want from your camera, what lenses you want for it, and then shop around for the best deals on either Canon or Nikon...I doubt you'll be disappointed with either.
That said, I selected Canon in the poll!
Cheers