Brian posted about the cumulative update for TFS (the TFS SKU, not the client/VS) back in June. After it was released we learned of a couple of bugs in it, including one where upgrades would not work in certain cases. Last Thursday, we re-released it with all of the known bugs fixed. We understand where we went wrong, and we apologize for the inconvenience.
You should apply this update to the server, build machine, proxy, and SharePoint extensions – all of the things that the TFS SKU installs. SP1 is a pre-requisite (i.e., this patch does not include SP1).
Today the .NET team is releasing a cumulative update patch. This has all of the QFEs up until a couple of months ago rolled into one patch. Included as part of that is a patch for WPF that improves the performance of the Windows Workflow Designer as well as a hang that a number of folks have hit. I had a few customers try it out, and they were happy with the improvements. I recommend this update to you if you work with the WF Designer (e.g., editing the workflow for Team Build definitions). There are still perf issues even with this fix, and the WF Designer team has made some very good perf improvements for the next release.
You can find a complete list of the issues fixed at KB 2468871 under More Information. There are also six features related to ASP.NET and Silverlight listed after the issues.
Here is the download page: http://www.microsoft.com/download/en/details.aspx?displaylang=en&id=3556.
P.S. This is completely unrelated to the TFS cumulative update that Brian has written about here. I recommend both.