This one causes a lot of heartburn for folks: you add a new instance in CF10 or 11 (in editions other than Standard, which do support adding instances), and you find that you can’t seem to have the web server configuration tool (wsconfig) connect sites to that new instance(s). You never see the new instance listed in the UI of the wsconfig tool. What gives?
The solution is relatively easy, and the problem could maybe be fixed (or at least warned about) by Adobe (and I just filed a bug report for it). Until that happens, I wanted to share this. For more, read on.