I have created new Gnome Shell extension called disable-window-animations. It's very simple. It disables all window manager animations like Window "slide-ins", Workspace "slide-ups" and "slide-downs" and many more... :-)

However it does NOT disable dash animations (Window-key "zoom-ins" and "zoom-outs" etc.)

I change workspaces very often and it was driving me crazy. There was no way of disabling it. Monkey patch did help here. Enjoy.