I have nothing whatever against Canon, but went with Nikon primarily because I have a bunch of excellent Nikon lenses. I shoot primarily with the D300 at the moment. While I greatly appreciate this fine camera, I don't consider myself a "Nikon-guy". I have a considerable variety of good cameras from other makers.

Unless there is a compelling reason to buy now, I suggest you wait until the successor to the D80 is announced. Best guess is that it will be announced within the next six weeks. No idea what new features or features will be upgraded, but at the very least, you will be able to choose between two cameras with contemporary technology.

Compatibility with your existing lenses depends upon the lens. If these are auto-focus lenses, you should have no problems. Only the very earliest lack the means of communicating distance to the camera. Nikon lenses made in 1992 and later have a D designation that does this. I would expect that third party lenses picked up on this pretty much at the same time. The only time this is a factor, is when using flash. The flash needs to use its own sensor, rather than the one built into the camera. Not generally a problem, but good to know.

If they are manual focus lenses - the equivalent of Nikon's AI or AI-S lenses, there is a problem. No metering - back to a hand-held meter. This might be upgraded in the successor to the D80, no way of knowing until it is announced. These lenses require at least the level of the D300 to fully function with the meter.

The other suggestion is to handle both cameras. The design makes quite a difference in the hand. A camera that fits your hand and has controls logically laid out, is a pleasure to use. If the designer's philosophy is not along the lines of your own, the camera will always be working against you. I expect that the D80s successor will feel much like the D80 does now. The differences between my D200 and D300 bodies is subtle. If the Canon fits you better, that should be your main consideration.

You have a couple of lenses, but not a huge investment in lenses. Had you an arsenal of excellent Nikon optics, that would be a fairly compelling reason to go with Nikon. Both cameras are highly capable, top of the line consumer cameras. As long as the camera is comfortable to use, you can not go wrong with either.