TFS Client API and 64bit Systems
I had a case recently where a someone was trying to develop an application which used the TFS Client API to connect to TFS. The problem was that the target machine was 64bit and the assemblies are 32bit only. The workaround for this was to create a webservice that performed all the functions the application required related to TFS on behalf of the application and simply passed the data to the application.
As the application tier can only ever be 32bit this is an elegant solution as it centralises all the data access and gives the developer and TFS adminstrator control over what data gets to the application. I will admit that this may not be a workaround for everyone, though with the 32bit only assemblies something worth bearing in mind.