In summer '99, I was a Hardcore FVWM2 User. An old wisdom says that you can spend a whole weekend customizing a FVWM2 titlebar, and I had done that.
I got a job at local museum - I needed to make a web page for them. I installed Debian on the work computer. Just for thrills, I didn't set up GNOME and fvwm2 for it - I picked Window Maker.
"Man, this thing sucks. It is... it is..."
Say it.
"...user-friendly."
Kind of disappointing to see a program that's easy to use, light, stylish, overall very pleasurable - than your current solution that you have spent hours and hours on, and it still isn't as cool.
I installed that to my home machine too. And haven't regretted that.
Window Maker is very easy to use and configure. Now, while the title bars can't be customized that much to make it look weird (you can pick between two kinds of titlebars, that's all), it's still aesthetically pleasing, and colors/bitmaps can be picked too. And theme support is there, right out of box (even automated theme packaging is there!). And as for all other configurations (window behavior, etc), those are there too. Let's just say that it is almost as configurable as FVWM2 - and configurations can be done with a text editor as God intended, or with an easy to use WPrefs.app or even more detailed separate application wmakerconf.
Window Maker's workspace support is pretty nice - the virtual desktop support of X has always been good and Window Maker doesn't make sacrifices. Alt+(number) changes workspaces, and the Clip (a widget that keeps application icons together; I believe this is called Fiend in NEXTSTEP) can be used to change between them, too.
For application launching, WM has an application menu (by default openable with right mouse button on top of the desktop). In Debian, it is automatically built from system menus, so that's always up to date without editors. Also, there's a Dock where running applications can be dragged to from the Clip and they can then be launched with a doubleclick. The Dock can also hold dockapps, that are basically small programs that run in dock. (Everyone loves asclock - yes, it existed before GNOME started it using as the panel clock =)
Overall, I think WM's app launching works better than any other application launching system I've ever seen; The Dock doesn't clutter the desk space, it stays down and doesn't obscure windows (unless you specifically want it to stay on top). Window Maker has learned its lessons from GNUStep and its heritage very well.
I use Window Maker with some GNOME tools as my primary desktop environment. It works very well.
It's stylish, it's easy, it's themable, it works well, it requires not much more computing muscle than fvwm2 - yes, Window Maker has been, as the slogan says, "my next window manager". Plus, it has a very descriptive name. =)