Absolute service addresses in .clientConfig
By default when you invoke Add Service Reference in Visual Studio, it will generate a .clientConfig file which contains the binding and address for the service you are trying to access. The problem is that the service address generated is always a absolute address, such as http://localhost:1234/Service1.svc. If you then take the web application containing the Silverlight .xap package out of Visual Studio and try to deploy it to a production machine, the absolute service address will no longer be correct, so the WCF calls will fail. The fix is simple, but annoying: when you deploy, you have to unzip the .xap package, manually edit the .clientConfig to correct the address, then zip the .xap file back up.
Part of the solution was already shipped in Silverlight 4, and is described in this documentation topic (check the section “Configuring the Service Address”). This feature gives you the ability to specify relative service addresses such as address="../Service1.svc". However the problem is that Add Service Reference by default will still generate absolute addresses by default. So the proposed feature here is to make Add Service Reference generate relative addresses by default. This way the address will always be correct, as long as the .xap and the .svc file are moved together.