Yeah it will be, thats just what I remember noticing from using both
Edit: From CameraLabs
So the EOS 50D essentially takes the 40D body and adds 5 extra Megapixels, a VGA screen, HDMI output, four times the sensitivity and a number of processing and interface enhancements. If you value these improvements, then it’s worth spending the extra or for existing owners to upgrade, but remember the body, viewfinder and AF are the same, so if you want a tough and quick semi-pro DSLR at a bargain price, the 40D remains a superb choice.
They are wrong about the AF, this is tweaked on the 50d, but those above are the main ones, like I inferred above, the other improvements are more subtle! But I think its something like this;
50d improvements over 40d;
* Faster processor (digic 4 over digic 3). One key factor for me - improves AF performance.
* More accurate AF - uses phase detect (as per 40d) and adds contrast detect for live view and face detect, if you want. Add the digic 4 to this.
* natural ISO up to 3200 (useable!)
* ISO expandable to 12,800 (at your peril, lol!)
* As mentioned AF adjustment
* Has in camera peripheral illumination correction (if you have a nasty vignetting lens!)
* ...and as mentioned the higher res screen (very nice it is too!).
* four levels of high ISO noise reduction (instead of off/on)
There are a few more minor tweaks, such as interface, creative shooting modes, auto lighting optimiser (dont use it!) and quick control screen but they wont make or break a camera.
For me the improved processing speed and AF was what made it for me as I do so much sports photography.
Dont get me wrong, I
really rate the 40d, lovely camera, but if you have the money the upgrades on the 50d make it worthwhile IMO.