The minimize to tray button would completely break the aero ui, nevermind the fact that it could not support proper theming. There already are programs (like NVidia's driver tools) that support adding such buttons to windows in this fashion. In the meantime, I don't see what the problem with Shift+Minimize is-- minimizing to the tray, if it's not already set in the options, seems like a power-user feature to me. A semi-out-of-the-way key combination seems like a fine thing for a power-user feature.
The UPnP suggestion is a good one, though. That should be added.