I just ran into a client's TFS configuration that, at first glance, caused a little concern. This client has a very beefy dual server TFS configuration including a clustered Itanium-based data tier. The client had previously tried to install TFS SP1 before and had painfully failed.
The original problem is that the Quiescence GDR that is required before installing TFS SP1 did not support clustering. Microsoft fixed that and the current download is actually a version 2 that does support clustering.
The second problem is that the existing installation documentation mentions Itanium exactly once: Windows Server 2003 for Itanium-based systems, and Windows Server 2003, Web Edition are not supported.
To summarize the story, Microsoft through product support and the product team, confirmed that there is a problem in the documentation and not the product. That is, the TFS Data Tier does support Itanium processors!
We did successfully and relatively painlessly perform the SP1 update to this TFS. There was one problem due to renamed service accounts which initially blocked the installation of TfsQuiesce on the application tier, but Dave Hope readily provided a solution for that!