Many pros are using Canon I think but at a lower lewel don't forget Nikon !!! And of course consider a good lens and a software. You have to take time to learn ...
Every trademarks are good but you have to consider to buy accessories you will keep even if you sell your dlsr one day, so try to stay with the same trademark unless you are rich ! I own a Nikon d300 and i love it, but my 70-200 is more expensive !
I know someone with a D40 nikon and a zoom who does decent pics.
Just tell us what you want to do with the camera and what is your budget !
