In a multi-monitor setup, deciding which monitor to place the panels on is pretty much a guessing game on either end: the user may not be aware of MATE's placement logic and MATE has no way of knowing which monitor the user would prefer the panels to appear on.
Therefore it is even more important to give the user a way to quickly drag the panels to the monitor on which they would like them. Unfortunately, this is currently a bit of a hassle:
* Right-click the panel and choose Properties.
* Clear the Expand check box.
* Drag the panel to the other monitor.
* Check the Expand check box again
* Close Properties
* Repeat these steps for the second panel
* At the start of the next session, curse because all formerly right-aligned widgets now appear in a random location on the panel (which I realize should be a separate ticket.)
Later incarnations of GNOME2 (e.g. the ones shipped with Ubuntu 12.04) had an easier way to accomplish this: one could simply hold down a hotkey combination while dragging the panel, without touching its Expanded state and without having to go through Properties. I'd love to see something like that in Ubuntu MATE.
What version of Ubuntu MATE?