I've been using them on and off, and the first thing I'd like to mention is that they're in no way magical -- both when it comes to using them (which is mostly knowing a few shortcuts and internalizing the layout system), but also in regard to how much they help you.
Sure, they certainly do look snazzy, especially when coupled with the movie hacker-approved unified dark color scheme. New windows pop up and quickly assume their rightful space and everything just looks so darn tidy.
But for certain usage patterns, that doesn't get you a lot. Even if you're popping up disposable shell windows left and right, you might also do that within screen/tmux, where the window manager doesn't come into play at all (or have some drop-down quake-like console). Also, your running applications and especially their different configurations might not change that often, in which case you're really saving yourself some manual layout fiddling once. So a lot of people would perform pretty much the same with just alt-tab window cycling and virtual desktops (which seem orthogonal to the whole deal).
I mean, if you look at the vast majority of screenshots, you don't even see that much work. The obligatory IRC client, fake-GUI music players and/or file managers and probably an editor with the configuration file or some minor coursework open. It's not exactly Scotty and his Mac Plus.
Having said that, I'd add my vote to i3wm, as it isn't as ideologically pure as some others (you still have window titles if you want them, and the layout remains somewhat manual). Plus a rather readable configuration format, even if the default configuration is seemingly intended to drive vi-users mad.
My alternative would be bspwm, the binary space partitioning wm. A lot more minimal, but the automatic layout algorithm is rather tractable and one certainly wouldn't be confused with too many options.