Multitasking doesn't work for me, using Loki. I've tried three fresh installs -- no joy. Everything else works great.
When I go to "multitasking view," I see only a single window, with no apps open on it. There's just the one icon below the window, with a "+" on it. But it doesn't do anything.
When I click in that single window, I just go back to the workspace in use. All the app windows reappear on it.
I had Freya installed on this machine before and multitasking worked fine.
I'm not happy about this, because I had gotten so used to the excellent way elementary handles multiple workspace.