Brad Abrams wrote an excellent post about how to set everything in the server and client to consume this services. He covers for areas:
2. Save personalization settings
3. Enable custom UI based on a user's role (for example, manager or employee)
4. A custom log-in control to make the UI a bit cleaner
These Services are simple wrappers to the actual providers and only provider the most common functions (i.e. Membership has login/logout, but not CreateUser), but would be pretty straightforward to extend them. If your application is not 100% SL and you have parts already build in ASP.NET you can easily combine them, for example, use the Login controls to Authenticate users, but use the Role Services to restrict certain functions depending on who is who.