Wikipedia's information about it confuses me. It says xcompmgr is a window manager, but it says it "does not replace any existing window manager". Does this mean it would replace AHWM, or that it would just add compositing to AHWM -- or something else entirely?

Also . . . what about it is difficult to "stomach"?

xcompmgr is a Composite manager. It will run along side any other window manager (that doesn't already do compositing... this excludes Compiz, newer KWin, Xfce4's window manager, but exactly what would happen if you tried to run xcompmgr and Compiz at the same time I don't know). It just does things like add drop shadows around windows and enable true transparency. {edit} You can configure the drop-shadows or disable them through command-line options {/edit}

I said 'stomach' because xcompmgr has been unstable at times in my experience. IIRC, none of the xcompmgr crashes have taken down X11 or the window manager. I have not used it in a while though so it may have changed, but I was under the impression that it doesn't get much work done on it. It's original goal was just to be a reference/example implementation of the compositing extension for X. I could be wrong though and it might be in a more stable state now.

If anything you might be motivated to see if there is a way to run it with debugging information. I can't imagine it's highly complex in the way that I assume Compiz is. It might be fairly easy to do some fixing up of it, as long as a person is motivated to look into it.

Thanks for the information. I think I'll give that a look on a test system, if only to see whether I care enough to bother.