Sorry for bumping an old topic, but this topic is interesting seeing that the forum was quite active 5 years ago. Everyone has a good reason why ending up with Fvwm. Personally, I don’t see any reason why not more are using Fvwm.
On www.slant.co I was reading the Top Con that Fvwm is: Old and complex, Tricky to configure with quite a learning curve, and Hard to be tamed. Maybe before, but today there are plenty of ready-made small scripts of functions and modules to get started.
Compared to other WMs that I have been looking at, they have nothing to offer to make them useful. Conky is a system monitor and beautiful wallpapers are for the eyes. If anything is missing in Fvwm, just make it. There is always someone to help. For example, it was great seeing how the Window Focus function was recently developed. This is why I end up with Fvwm. 