I might get flamed for this but as a developer I would like to confirm these with other users before I add yet another bug report to the ever growing pile.
starting with an update in Fedora 7 the print screen button in Gnome stopped working for a mutli monitor setup and only captures the leftmost monitor for a screenshot... the shot itself is the same width as all monitors, however all monitors to the right are black in the screenshot. (taking a desktop shot with Gimp works as expected)
the fact that this has been around for over a year means either: its not a bug but something in my settings, or my theory that the devs never consider multiple monitors is correct
on another note.. I don't think anyone at Nvidia has multiple monitors with mixed GPUs because at one point their drivers stopped allowing 3d to run across multiple mismatched GPUs, it used to work, then after a driver upgrade and every driver after that.. .it stopped working.. Nvidia's response to a bug report: "You cant do it with mixmatched GPUs, if it worked in the past you must be imagining it" my response: "then why does it work in windows, and with older Nvidia drivers?" Nvidia's response: "..."