TLDR: i3 is definitely worth learning to use; it is an outstanding window manager.
I use/used many desktop managers (spent considerable time with gnome (2.x and 3.x), lxde, xfce, and enlightenment17) and played a bit with several window managers (openbox, awesome, xmonad). i3 started with an already excellent window manager (wmii), but then blessed it with that final bit of intellectual consistency and rock-solid performance that a power user wants in such a critical part of their workflow. i3 has been my window manager of choice for several years, and I don't feel the smallest itch to change. When I'm trying to get work done I need all my screen real-estate, and I need my windows organized. I get this for free (it just happens as I open applications). If I want windows organized in a particular fashion, it's no more than 2 or three intuitive keystrokes away--I can completely organize my desktop in less time than it would take me to grab my stupid mouse to go and begin the arduous process of grabbing window corners and resizing all the windows under a more traditional window manager. Whenever I have to use traditional window managers I am amazed at how inefficient they are!
There is a learning curve associated with using a WM like i3. For instance, you need to already know how to start via commandline all of your applications or write something to parse and organize all your system and local