There are times that I need to get my hands dirty fixing problems all by myself, then telling everyone else how to do it. Then, there are times that I post a blog entry complaining about something or other, and the solution finds me. This, thankfully, is one of those times.
While I'm definitely an OS X guy for the moment (don't screw it up, Apple... please), I was relatively upset about the essentially useless X11 code in Leopard, and posted about it this morning. This afternoon, I received an email from Tevor Zylstra with a pointer to the Leopard and X11 blog, which contains links to the Xquartz Project. There, I found an unofficial X11 2.1.3 release that fixes all the bugs I've come across with Leopard's X11, from the window focus to the Option-click pasting. Huzzah!
Either I need to do more research or less -- I'm not sure which. All I know right now is that I'm a happy guy. Many, many thanks to Ben Byer and his group. Hopefully, 10.5.1 will incorporate this update and make it official.