A friend recently bought a high end Nikon digital SLR and it's incredible. I don't know what model off hand, but Nikon makes an excellent camera. One thing is, if you buy the Nikon, it doesn't come with a memory card and the internal memory doesn't allow you to do certain things from what my friend said.
Canon's DRebel is IMO a more than adequate camera and well under 1000 bucks. I've had it for over a year and am very pleased with my results. And now that the 20D is out, 10Ds have dropped significantly. It is considered by many (including some Nikon people) as THE prosumer DLSR.
Before this degrades into a Nikon vs Canon thread, just take into consideration that the technology is so good on all levels that you really cannot go wrong in any system you try. There are pros and cons in any system and it all boils down to your own personal preference. What exactly do you plan on shooting?
Whatever you choose, be sure to pick up some good glass. I don't care if you get a 1DS markII, crappy lens = crappy pictures.