If you're an fvwm user, you will probably lament the documentation of Awesome. Configuring anything in Awesome required reading the Lua API docs, which in my experience left something to be desired. I found it interesting that Danjou said Awesome is nearing maturity, because I didn't think the docs were one of a mature application.
Fvwm on the other hand has superb documentation. Having used GNOME, KDE, xmonad, awesome, and a little bit of fluxbox, I have landed on fvwm. It has the best documentation, the most stability, and the least bugs--zero that I have found. Xmonad was nice but it practically required keyboard usage--it's hard to even configure things like window decorations. I like the keyboard but the mouse shouldn't be second class. I found some bugs in xmonad that would cause the window manager to completely lock up. Awesome's documentation is not the best, and it suffered from bugs as well--I had some problems with decorations on floating windows, for example.
The only thing I miss on fvwm is automatic tiling. However, FvwmRearrange allows tiling at the press of a button. Since I now use a lot of desktops (20) I find I don't have much need to rearrange windows automatically because each desk has the windows arranged as I need them. FvwmPager makes it easy and manageable to use a huge number of desktops.
If you already know fvwm I don't think you'll gain much from trying awesome. I also urge new users to try fvwm. It's not very hip--maybe because it is old--but for configurability, stability, and documentation it can't be beat.