I cannot recommend attending the pre-conference sessions. At PDC05 I attended PRE03 presented by Brandon Bray, Anson Tsao and others. Anson had some gems in his slide deck that I really wanted. There's a problem, though. Microsoft presenters believe that the slides and everything will be available to attendees on the DVD afterword, so they don't bother printing them out. But that's wrong. Indeed, in the conference guide for PDC05 on page 39 it says "Pre-conference sessions, Hands-on labs, and keynote/general sessions are not included".
Even after pestering the presenters with email after the DVD arrived, I never got Anson's slides.