The most important thing for me is to remember you are buying into a system, it's not just the body that you should be concerned with. It's the lenses, flashes etc that work with that system.
Do you have any friends with cameras?? If so this provides you with an option of borrowing each others equipment, which is always a consideration!
I know I started a thread on here when I first joined and I have seen countless others on here since about upgrade paths and nearly everyone says it is better to upgrade the lens you are using than the body. I have a Canon 30D and have upgraded to some expensive canon 'L' glass, and my results have improved considerably, much more than if I had bought another body.
If I were you and if I had my time over again, I would initially buy a good used
second hand body, and to be honest if you were thinking of doing this a Canon 30D wouldn't be such a bad choice! It's a nice size and weight, magnesium body and a solid feeling camera. Nikon wise a D80 may be a good choice as a comparable camera and if you were to buy used then you will not lose a huge amount of money if you decide photography is not for you and sell up.
In terms of not using all a cameras functions, only you yourself know what type of person you are and whether you have the time to learn. If you feel as though you are not going to bother learning about Aperture, Shutter Speed, Depth of Field, ISO and their relationships then my advice would be don't waste your money on a DSLR at all, as it would be like owning a sports car and not taking it out of first gear! If on the other hand you like learning new things, keep reading and posting on the forum (it has some amazing photographers) buy one and jump in - the waters lovely!
Welcome to the world of photography, it's addictive and a licence to spend all your spare cash!!!!!
Hope this helps and let us know how you go on!