I'm running ObjectDock on a laptop with an extra external monitor.
Everything seems to work fine if I leave the dock on the primary monitor, but I've run into a couple of problems if i move the dock to the second monitor. Biggest problem is that I cant drag icons anymore. I can pick them up, but dropping in a different location just causes them to fly back to the original location. new shortcuts can't be dragged onto the dock, and nothing can be dragged into the recycle bin. I can drag icons off the dock to delete them though.
Aside from that, spacers seem to leave artifacts in their location on the opposite monitor, and a dock placed on the border between monitors slides onto one when it autohides on the other, though I realize thats more of an issue with windows than ObjectDock.