Recently, I realized that the titles of my windows have been getting longer and longer, and the windowlist has been getting less useful by the same margin. Right now, I end up seeing, for example, 12 windows with "The Titl...Konqueror", which makes figuring out which window is which a process of trial and error. Anyway, I wrote a patch to allow the width to be configured. It is against SVN as of right now.
Created attachment 830 Configurable windowlist width for SVN
Sorry, Xfce is in feature-freeze for 4.4.
Actually, thinking about it again, this is just pref-bloat. It's impossible to tell whether the "important" part of the window title is at the beginning, middle, or end of the title, nor how much of the title we actually need to show to be useful, so there's no good default for this. I also don't want another "override system setting" pref.