Leopard software issues
If you are thinking of upgrading to Apple’s new OSX 10.5 (aka Leopard), you might want to take a look at this post on MacFixIT (and all it’s comments) to see if any ‘important to you’ apps are on the no-fly list.
I haven’t had any issues since doing a clean install on my iMac, but I also haven’t really done much reinstalling of software yet. My Powerbook is still running Tiger with all the ‘mission critical’ stuff humming along fine.