In my case (blessed with not having to work with Windows), the kludgy feel of how workspaces previously worked with multiple monitors has sometimes made me not bother connecting them up.

The old way tries to merge the two monitors into a single screen, and so when your monitors have different resolutions, your "single screen" is now sort of L-shaped. Which would cause weird effects on some DEs where for instance dragging a window off the edge of the smaller monitor wouldn't work, as width of the "single screen" was taken to be the width of the larger monitor not the smaller one. (I must add that KDE is not one of these DEs, and you can drag off the edge like that)

There are still some behaviours with per-screen virtual desktops that I hope might be fixed in future - such as "Zoom Desktop" (Meta+mousewheel). I use this quite a bit for reducing the black bars on extra wide aspect ratio films, and it does zoom both monitors at the moment. I don't know if it'd be practical to have this feature just zoom one desktop, but it would be great for me when I'm working and have Netflix on at the same time.