For the next release, Sawfish should be configured so that the focus click is "eaten" instead of going through to the application. Then you can focus apps without having to microtarget the window border.
On the other hand, on the GNOME bugzilla we have people complaining about them unknowingly having pass-through-click set to false and buttons in unfocused appliactions not working. What is the problem, really? I.e. which applications do you need to micro-target? What does Windows do? I think this is the really important question.
Windows does pass through, Mac does not.
You're probably right though: http://discuss.fogcreek.com/joelonsoftware/default.asp?cmd=show&ixPost=1793
Experiment with Metacity demonstrated that pass through is required unless you are "application-based"