I recently upgraded to Leopard on my work MacBook Pro. In Eclipse, one of the first things I ran into was anytime I tried to do Open Resource (Shift + ⌘ + R) to open a file resource, Eclipse would crash with a nasty exception.
Exception Type: EXC_BAD_ACCESS (SIGBUS)
After doing a bit of googling, this seems to be a bug in SWT for Leopard (see here). I upgraded my Eclipse to the 3.4 Stream Stable Build found at http://download.eclipse.org/eclipse/downloads/ and my problems have seem to gone away.
It's got a pretty cool new splash screen too :)