I've been using Windowmaker since the late 1990s. I've run it under Solaris, Fedora and now Ubuntu. It's **fast** and things load quickly. I mostly launch things from the menu tool you access by right-clicking on the screen. It's easy to add apps to it and it takes up no space on the desktop. I don't bother with dockapps myself.
Windowmaker is very much a mouse-centric system. I'm a boomer and mousing is the way I like to work.
The feature which sold me on Windowmaker was the ability to drag a window from one screen to the next, or to just move it by with a right-click in the top bar and choosing which screen to send it to. The only real downside I see to Windowmaker is that there's nobody to really teach you what you can do with it and you have to fool with it to discover what it's capable of.