If you've played with the beta of Team Foundation Server 2008 (formerly code-named "Orcas") then you may have noticed that the process templates are versioned MSF v4.2. I wondered what was different about MSF v4.2 vs. MSF v4.1 so I asked Sanjeev Garg on the patterns and practices team. Sanjeev explained that there really aren't any noticable differences in v4.2. Mainly the changes are some behind-the-scenes bug fixes and better support for localization.
Oh, and in case you're still using MSF v4.0 and you're wondering where MSF v4.1 came from, this was the new set of MSF guidance which was introduced when Team Edition for Database Professionals shipped at the end of last year. It adds two new roles to the process guidance, one for Database Developers and one for Database Administrators, along with the corresponding workstreams for those additional roles. Note that MSF v4.1 introduces changes in the process guidance only, it doesn't change your work items or other artifacts. You can find out more about upgrading from MSF v4.0 to MSF v4.1 here.