With a 2.4 MBP w/4 GB RAM:
On occasion, after installing Leopard, upon waking from sleep, my keyboard will suddenly register a key as being permanently pressed, resulting in an inability to do much of anything except listen to the repeated bebebebebebeep of a key pressed incessantly. Sometimes it's the shift key; other times it's a number key, or the Apple key. It has been the semicolon key, the "p" key, and the Tab key. When I open the Keyboard Viewer, it shows which key or keys are being registered (thanks Tech support for showing me that feature). When I sleep the computer again, it sometimes stops once I wake it up again. Other times, it will quickly start happening again and will take another sleep-wake or a restart to function normally.
During all of this, the trackpad seems to function normally.
It doesn't seem to have increased in frequency, though the first few days it happened (around 11/6) it occurred 10x or more per day. Now, it seems to occur about 3-4x every few days.
The keyboard is functioning normally otherwise, and the hardware seems to be fine. (Read: there are no ACTUAL stuck keys!)
I understand it's unlikely anyone will be able to solve this problem, but I'd sure love to know if anyone else is experiencing this after upgrading to Leopard.