Remembering e17 makes me extremely nostalgic - in fact, if anyone has a screenshot of the clock circuit-board background with the working 7-segment clock on it, I'd be eternally grateful.

It was lovely to use in the very early days of amd64 as a window manager (along side gtk and kde libs). My absolute favourite was the virtual-desktop handling with multiple physical monitors in that you can switch between virtual desktops in a screen-independent way. Nothing else I've used has hit the same seamless ease.

i3 does this well. Switching to a virt. desktop on another screen switches to that screen by default but you can also move virtual desktops from screen to screen, e.g. "move this desktop with all windows to the screen to the right". It should also be possible to configure a shortcut for "move desktop x to current screen". Personally, I find explicitly moving desktops more intuitive.