I'd be shocked if you didn't know this already Brian, but just in case… You can turn off the OSD pop-up bar altogether by disabling the checkbox for Enable OSD under Tree & View/Advanced.
If you still want to show it for other reasons, the OSD can be made visually appealing by setting the Pop-Up Transparency Mode to Enabled under General/Advanced. That said, changing the setting to Enabled will make ALL pop-ups (menus, tooltips, and track info) transparent as well. I personally love transparency for all pop-ups, but if you don't, then your stuck with the gray OSD.
I realize that none of this solves your desire for a remote control command to show the Pop-Up Player Bar (the "playback strip"), but figured it was a good opportunity to provide information about the OSD that people may not be aware of. I personally did not discover how to get rid of that supremely ugly gray for the 1st couple of years I used MC, so I presume others may be in the same boat.
One final note for Matt: There are 3 modes for Pop-Up Transparency: Enabled, Disable over Movies, Disabled
The Disable over Movies mode does nothing. When checked, all pop-ups (the OSD, right-click menus, etc.) all remain transparent, so effectively there are really only 2 options for transparency: Enabled or Disabled. I personally think that's adequate, but having an additional option which does nothing is confusing for new (or old) users.