Open Transport vs. QuarkXPress -- I've heard reports of two conflicts between Open Transport 1.0 (shipped only on the Power Mac 9500s) and QuarkXPress. If you have an XTension installed that receives the XT_NETRECEIVE opcode, QuarkXPress will hang on launch. I doubt there's any easy way to determine if you have such an XTension loaded other than by empirical testing. Apparently, Open Transport 1.0.1 fixes the problem. Even with Open Transport 1.0.1, if you have either the printer port or the modem port chosen as your network connection in the AppleTalk control panel, QuarkXPress will hang on launch if any XTensions that use network serial copy protection are installed. [ACE]
Wake On Demand in Snow Leopard
Putting your Mac to sleep saves power, but it also disrupts using your Mac as a file server, among other purposes. Wake on Demand in Snow Leopard works in conjunction with an Apple base station to continue announcing Bonjour services that the sleeping computer offers.
While the requirements for this feature are complex, eligible users can toggle this feature in the Energy Saver preference pane. It's labeled Wake on Network Access for computers that can be roused either via Wi-Fi or Ethernet; Wake on Ethernet Network Access or Wake on AirPort Network Access for wired- or wireless-only machines, respectively. Uncheck the box to disable this feature.