The news is rapidly coming out about Apple's latest OS, Leopard, and hardware and software compatibility problems.
I'm not going to list them here, they're all over the Internet. What I will say is to check every hardware and software vendor of products that you own for Leopard compatibility BEFORE you upgrade or even buy a new Mac.
There's nothing new about these types of problems. This happens every time a new OS is released no matter who the vendor is.
Erik