Marc Shepard, a Program Manager for Microsoft in the US held a session at Tech·Ed Orlando this year about how to upgrade from SUS to Windows Server Update Services, the next version of SUS. I know this session was highly rated, and I've already listened to it from the conference website. If you don't have access to this, but want to know more about, Marc will be re-delivering this level 300 session as a webcast on 16th August between 11:30 and 13:00 Pacific Time. Unfortunately, this means it's a 19:30 UK time start, but worth it (IMHO). You'll get a chance to learn about the best practices and pitfalls to watch out for when you get round to upgrading your infrastructure, as well as ask your all important questions.
Registration is here.