In my experience, KDE works well and gets out of my way, while gnome does stupid shit and is non-configurable. I don;t have multiple monitors with different refresh rates so I can;t comment on that, but I do not run into bugs in KDE often at all!
(I mean I did accidentally lock up my computer by opening several hundred copies of the screenshot app, but that was my fault - I accidentally put a banana on the print screen key!)