Thank you sir! May I please have another?!?
If you're not the crafty sort, you'll wonder "why?" The key cause for worry is in this paragraph:
In addition to the POSIX and math libraries supported in Tiger, Leopard enables developers to build complete 64-bit applications using the Cocoa, Quartz, OpenGL, and X11 GUI frameworks.
Guess what's not mentioned there? Carbon. That's the library that virtually all developers of audio software on the Apple platform use. You may not be intimately familiar with it, but suffice to say that Live, Cubase, Nuendo, ProTools, and even their own Logic are all written against the Carbon library. No 64-bit Carbon means no 64-bit audio apps, until all those developers port their various products to Apple's ridiculous Cocoa library and everyone learns Objective C.
Now, it's not as bad as all that. 32-bit Carbon will certainly be present in Leopard. (If it wasn't, roughly 95% of the apps written for OSX wouldn't work with Leopard.) But I wouldn't hold my breath for the next iteration of OS X having any 32-bit capabilities at all. It's not something you need to really worry about right this minute, as a user, but I'll state right here and now that if Carbon ceases to exist at all, it will effectively wipe out indie development for audio on the Macintosh.