You might already have been in the situation where you wanted to unshelve a stored shelveset when having local changes to files that were also changed in the stored shelveset. Out-of-the-box with TFS 2008, this is not possible and you will get the following error dialog :
Your local workspace may not contain pending changes on files that are included in the shelveset. However, there is a way to unshelve with local pending changes. Therefore, you need to have the Power Tools installed for Team Foundation Server.
From the command-line you can execute the tfpt unshelve command with the name of the shelveset to accomplish that.
tfpt unshelve allows a shelveset to be unshelved into a workspace with pending changes. Merges content between local and shelved changes. Allows migration of shelved changes from one branch into another by rewriting server paths.
Like in a normal get latest scenario, you will be asked to resolve conflicts and eventually be redirected to the well known TFS merge window.