Its the little things in a new camera that really make a difference. Anyone that has ever had to navigate the menu system on the EOS 10D, 20D, 30D or 40D will love the new Quick Control Screen feature on the EOS 50D. If you feel the Canon menu system is complicated you should see what Nikon owners have to go through to set certain functions.
To access the Quick Control Screen all you need to do is press the multi-controller and use it to navigate to whatever function you want to change. Then use the Quick Control dial or Main dial to change the setting. And once you half-click the shutter the Quick Control Screen goes blank. This is especially helpful if, like me, you hate tilting the camera to see the top LCD panel when shooting.