I have been a happy user of AwesomeWM for years. I don't actually use the tiling layout all that much (I definitely do use it occasionally and find it useful, but usually I'm in floating or "monocle" mode). But in additional to tiling support, it is minimalist, keyboard-driven and infinitely configurable through Lua scripts which I really like. I think a lot of other tiling WMs are probably popular for similar reasons.
I've been an awesomewm user for quite some time as well and have no plans to change.
It's the lua scripting that really pushes it to the next level for me. I think I fell in love when I set up randomized times wallpaper rotations, and then realized that I could also create multiple profiles/sets of wallpapers as well, and the only limit was my own ability to add it.
