The MacBook that I work on every day is running 10.4.11, but we bought a new iMac desktop for the house on Black Friday and it came with Leopard preinstalled (*).
Got the iMac out of the box, set up, configured, etc. and brought the wife in to show it off to her. She noticed the remote control (which her older iBook doesn't have) and asked what it was for. So I fired up Front Row and handed her the remote control to play with it. She navigated to the "Photos" section, selected an album and clicked "Slideshow".
And that's when the screen went blank and the iMac locked up. I mean, it locked up big time, as in requiring me to power it down. I thought it was a fluke and so I went through the process again -- it's definitely a repeatable bug. A subsequent search of the Apple Support forums indicated that other folks were having similar problems with Front Row under Leopard.
Now, to be fair, other than
that I haven't run into too many problems with Leopard. But my wife is now afraid to touch the remote control for fear that she will "break the computer" again.
(*) Well, OK, it wasn't in fact preinstalled, but I felt like that was a good machine to experiment on since we were starting from scratch there.