i3

Fast, well documented, easy to learn and configure.

Best tiling windows manager on the planet period! If you have multiple monitors, this is WM to have and use.

PROS

• probably the easiest dynamic window manager while also being feature-rich.
• defaults are ok to begin with
• very good documentation for users
• very and easily customizable
• has all the major container layouts out of the box: tiling, tabbed, stacked, floating
• plust it has the very useful scratchpad (and sticking of windows)
• resource usage is ok
• has good performance
• you can create customizable layouts

CONS

• there are some annoying bugs related to the layouts
• no way to restore sessions; however it's possible to create the customizable layouts (which has some degree of automation but still needs manual intervention) to sort of try and recreate those sessions
• it will die with Xorg

I was skeptical at first of how well a tiling window manager would work, but decided to give it a try (with a base Debian MATE environment), and it has worked surprisingly well, allowed for every customization that I've needed, and has greatly improved the speed of my workflow. Color me impressed!

It's the best tiling window manager for my needs. Great documentation. Great config file syntax. Great performance.