I recently bought myself a Canon EOS 500D also known as EOS Rebel T1i, and EOS Kiss Digital X3. I also got myself a Canon EF 50mm f/1.4 USM lens.
One of the new things about the 500D, compared to my previous 400D, is that it has live view. So I wanted to see if that's useful or not. I'm not that happy with it. If you want to let it auto focus normally you would half press the release button but instead you need to press the AE lock (*) button, half pressing the release button doesn't have any effect. The live view auto focus is also very slow, takes about 5 seconds on average. It's also has a habit of not focusing it all, or going in the wrong direction to find the focus. I sometimes suddenly feel the focus ring vibrate on the 50 f/1.4 USM while it normally never moves. There is also some weird clicking noise on my zoom lens, it appears to keep trying to send it beyond the smallest focus range while the object is meters away. There is also a "quick" focus mode, so that if you press the AE lock button the mirror goes down, temporary turning live view off, doing the focus the normal way, and then the mirror goes up again. In that mode the auto focus takes about 2 seconds instead. The only thing live view seems useful for is that you can zoom in to see if something is in focus.
I'm also seeing some weird behavior when using the flash. When using the 50mm f/1.4 it really seems to prefer using f/2.8, sometimes f/1.4 or f/4.0, and you can't select anything else in the auto, CA or P mode. Sometimes the depth of field is just too small, so I tried to set it to Av mode and manually select the one I want. What I didn't expect in that case is that it's calculating the shutter time like it won't be using the flash, and you suddenly get shutter times of 5 seconds. Other modes have similar problems, only setting everything manual seems to work properly.