Indeed, one of the main reasons I switched from Budgie to Gnome and later to KDE was the lack of multi-monitor support. I for one am really excited to see what they come up with for Budgie 11 because honestly I think Budgie is my favorite desktop, it just has a couple problems that make it hard for me to use at the moment (mostly just multi-monitor support really), and if they even get semi-addressed I'll probably switch back to Budgie (assuming I haven't completely fallen in love with qt apps by then).