A few months ago, there was someone with the same question. I mentioned to him that the XTi is good in it's own right, but, moving to a 30D would be better, as it would allow him to grow into it, and further into photography as his 'skills' became better. As of right now, he has added quite the lot to his collection, and seems to be enjoying his camera just as much as he did his point & shoot.
I say go with the camera that YOU feel is going to be the better choice. If you will be the one using it, primarily, I say get what you feel is the right one. Otherwise, you may regret it later on...
Oh, and yes, glass (i.e. lenses) do make a really big difference. However, the kit lens that comes with the 30D/XTi is a great lens to start with, to understand what you like to take pictures of, and where you will be taking them.
Good luck, and a warm welcome.