Dilemma

I now have a Canon Rebel XT. It's a great Camera but I'm ready to invest in something new. I plan to sell my current camera and use the money to invest into my Next one. Here's my dilemma, I've heard good things about both the EOS 40D and the EOS 5D. The 5D is over $1000 more and I'm curious if anyone out there has any experience with these cameras and could tell me if the 5D is worth investing the extra money into. I'm not dead set on buying Canon and I am open to info on all DSLR's. Advice would be much appreciated.