Because XMonad is library for writing your own window manager rather than just a pre-built window manager. That means that everything will always work exactly how you want it to because you're the one programming it.

Also, awesome used to crash a lot.

I don't use awesome myself so I don't know about it crashing, but it appears to be a base to build your own system from, in the sense that most of the functionality comes from extensions written in Lua.

Musca, my window manager of choice currently (though I am beginning to try out others too, just in case I'm missing something), is a very small WM with very few features, but a very simple way of extending it through scripting (in any language).

Musca itself is tiny: little under 4K lines of C (including whitespace and comments), the binary is about 190KB. It delegates its "menu" to dmenu. If you want anything else, you use external scripts or programs.

Well, personally I switched from AwesomeWM to XMonad and the main reasons were that I liked the way that XMonad handled multiple screens better, compile time checking of the configuration file, and better community documentation (though awesome's is decent).

The default widgets in awesome are nice, but if I'm going to be using a tiling WM as a drop in replacement in a desktop environment I just have to remove them in the config file.

Am I the only Ubuntu user that likes Unity? Then again it could just be because it reminds me of Macs and a Mac is my main machine.

I wanted to like Unity. However, until Ubuntu 12.04 it always was very slow.

In the past, I've found that compositing desktops (as implemented wit Gnome over the years, and now Unity) would interfere with some applications. I would assume they also interfere with games that want to use the GPU heavily. So, I spent quite a while trying to use Unity2d. While I was able to badger it mostly into working, it always felt very second class. On 12.04, it feels even more second class, and of course it is going to be removed in 12.10 anyway.

I do like the idea of a side bar. When I use OSX, I put the dock on a side. When I use Windows 7, I put the start bar on the side. I also love the idea of the HUD. On OSX I use Quicksilver, and on Windows I navigate the start menu by searching it. In the past I've used Gnome Do. When it comes to Unity's implementation though, I've found making .desktop files for applications I want to use that don't already come with them to be cumbersome and error prone. If I don't make a .desktop file, I can't launch it from the HUD, nor can I lock it to the launcher.

When it comes to altering the menus to place the menu bar at the top, this is a decent idea, but again the implementation feels poor. I don't like that the menus disappear until you hover over the bar. That makes it hard to know where I will want to point the mouse until I get over the bar to make it show me the menus. I suspect that this is one of the changes that makes this such a large fork of Gnome 3 BTW. I would have prefered that they put out a proof of concept first, then try to work with Gnome and GTK to make it an option that is merged in.

Despite all that, I still use Unity since I like Gnome3 and KDE even less. I recently tried LXDE and XFCE, but I they seem like an unpleasant jump back to the 90s. For one thing, I don't want to go back to managing my Start/Application menus, I want to keep search. For another thing, I like largish icons on the left or right.

I am currently watching the Cinnamon project. I think they look promising. I haven't gotten around to trying it out in a VM though.

There's also a substantial Awesome user base at Google; I think the choice of tiling window manager is largely based on peer usage.

Not at Google, but: I chose xmonad when I was making the switch because it seemed to be the most stable of the tiling window managers at the time.

I've stuck with it mostly out of inertia; I don't actually know much Haskell.

I avoided awesome because I'm not a fan of Lua. Not as a matter of ideology; I just don't enjoy working with it.