I often find my self moving around windows on the screen and realizing that
I want to place the window on a different workspace. I then have to let go
of the window, rightclick on the list and select workspace or try to use
the very small window in the pager, then I switch to the workspace I moved
it to and do the adjustments. I don't find this very optimal. 

When I drag a window and hit's the edge of the screen it should switch.
Maybe a adjustable (from gconf-edit) delay before the switching to avoid
accidental swithing. However I almost never drag windows and hit the edge
of the screen, not wanting to switch, so I don't know about the delay...