Hey Todd,
When CA released the multi-socket listener, Garanti Technology out of Istanbul did some extensive benchmarking and volume/load testing; the lead Garanti Engineer presented the process and findings at a CA World session.
I don't have a copy but Lynn Williams or Jean Rissmiller from CA may recall the session and be able to locate a copy for you.
In short though, it is higly scalable and absolutely the superior architectural solution. Hope some of that's useful,
Tim