my 2 cents worth
First of all, please consider your system - one you decide on one, buy good lenses and stay within that system. I have worked with canon for 25+ years, so you know which system I pick...
If you are interested in video, want the cheapest price and don't need all the bells and whistles, then Canon is just now coming out with their updated Rebel series - almost identical software and sensor to the 50D with video capabilities as well. It also has the similar focusing as the 50 which is an improvement over the previous rebels. It is sub $1000 with a lens. Pretty sweet.
I've owned the 20, 30 and now the 50D's. Image improvement has been amazing with each jump, and low-light capabilities are amazing. 3200 ASA on the 50 is comparable to 200 ASA on the 20D. The 50 offers several advantages to the 40 I appreciate - the biggest being the micro-adjustment. Cameras that get used a lot DO go out of focus in a minor way, and if adjusted within warranty are freely adjusted, but once out of warranty run @ $215 or so to fix. The ability to do that in camera is huge if you are particular and will hold the camera for a long time.
Cameras are a lot like macs - get the best and newest you can afford, and hold onto it, no looking back. But know what you are getting into and what you want to use the camera for, and what your abilities are - you may find that newest rebel is your best deal. - email me if you want more specific details.
Steve