As above really, the 1000d is ok as an entry level body, but that's exactly what it is, entry level. The 450d is a cracking camera, but again is pretty much entry level, but with the right glass you can get some great results. It's what I use and can't fault it. 50d is where I would start now if I was starting out, although a bit pricier, a much more capable body.
The best advice I can give though, is go to a store where you can handle each body and see what feels right in your hands. I tried both Canon and Nikon and found the Canon to feel better for me, as you have to remember, it will spend a lot of its time in your hands and you need to feel comfortable with it. So go have a play and see what you like.