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]
Disable Caps Lock
If you find yourself pressing the Caps Lock key accidentally as much as I do, note that you can disable it entirely in Mac OS X. Open the Keyboard & Mouse preference pane, click the Modifier Keys button, and in the dialog that appears, select No Action from the Caps Lock pop-up menu. You could remap it to another modifier instead, but that might make using differently configured Macs more difficult.