The nicest things about a tiling manager? You can control nearly everything from the keyboard. It's very quick and easy to set up side-by-side windows (or side/top-bottom, and so on), and resizing one automatically resizes the other. It really helps on smaller screens, since by default everything is full screen with minimal window decoration.
Some nice features of i3wm in particular - well developed manual control, most layouts can be expressed as the composition of simpler layouts, and the config file is just a config file, not a full fledged program.
Also, it's worth remembering that on Linux you can have multiple WMs installed at the same time. You can log in to i3wm, and if there's something you really can't figure out, you can log out and switch to gnome/kde/etc. I don't know if there's a way to switch WMs without shutting down the whole x session though. Would be interested to know if it's possible.