J. B. Rainsberger has written an excellent article about the usefulness of planning velocity (and the places where it is not useful as well). I highly recommend reading it, particularly if you are a manager or a project manager.
Agile Advice – Working With Agile Methods (Scrum, OpenAgile, Lean)
All Things Agile: Scrum, OpenAgile, XP & Lean
Thanks so much for the recommendation. Google will help people find it more easily if you change the spelling of my name to “Rainsberger” from “Rainsburger”. Take care!