As I mentioned earlier we now support running TFS service as network service. The primary advantage of using network service is, you don't have to worry about managing the password for the account. If you are using VS 2005 TFS running under domain account and want to move to Orcas with TFS Service running under Network Service following are the steps.
Steps to upgrade TFS 2005 with Domain account to Orcas with Network Service
Now you should have your Orcas environment up and running with Network Service.
Please give us your feedback. Is this good enough solution or do you want us to improve this experience.