2. The exposé bug: Use exposé to reverse the order of windows, click on the top one, and the one below pops forward. Sorry, I just realized I have not filed a bug report for it. You asked me to file one at bugreport.apple.com. I asked if you were sure you wanted it there and not at macosforge.org, but never received an answer, so I forgot about it.
Report it both places if you're not sure ;) I'm not sure I remember this issue since I've been using exposé without a hitch, so please file the bug to remind me and get it in my queue.
3. Not a problem but a question: I haven't reinstalled Xquartz-1.4.0-apple7 because (a) I have no time to test it anyhow, and (b) I don't know if the Xquartz with 2.3.0-rc3 supersedes it, and (c) I don't know where to put it. It appears that /usr/X11/bin/Xquartz and /Applications/Utilities/X11.app/Contents/MacOS/X11 have traded places? Looks like the former is now just a thin wrapper to start the latter. Should any future Xquartz releases be installed on top of the latter?
Yeah. 2.3.0-rc3 has 1.4.0-apple13 (check X11->About X11). If you want to drop down to 1.4.0-apple7, you'll need to put back the old X11.app as well (your safest bet is to just reinstall 2.2.1 and drop in the binary). I think the server bits entered the .app bundle around apple8 or apple9 (which is why I haven't really announced the incremental changes).