We have begun using the following branching structure in TFS 2010:
Take a look at Jacob Ehn's blog post Automatically Merging Work Items in TFS 2010. He wrote a plug in that can be downloaded from codeplex. It will automatically associate the work items that were associated with the merged changesets. So when you merge to Main or Release the work items will be associated with the changesets in those branches, and the work items will be included in the build reports for builds off of those branches. The plug-in is super easy to deploy.