And here is some more guidance around SBS migration, posted by Nick King, Senior Technical Product Manager for SBS at Microsoft:

Recently I received the feedback that we needed a better way of representing all of the tasks during the SBS 2008 migration process.  We spent some time looking at what could be done to support a smoother migration, and came up with this document for partners and IT Pro’s.

Migrating from Windows SBS 2003 to Windows SBS 2008, guidelines and checklist

This guide is designed to be your step by step companion during SBS migrations and includes feedback and insight from our Support teams, MVPs (Susan Brady, Wayne Small and Eriq Neale)

While you’re migrating you should also check out these great resources;

Technet SBS migration docs

Practice you migration with this click through demo

Or check out Jeff Middletons third party swing migration

Nicholas King : SBS migration guidelines, training tools and checklist