Up until now most service packs meant something was missing/wrong. The name service pack was associated with bad software. It looks like that is bound to change. More and more software vendors are using service packs to actually introduce new features to their products.

Latest example of this is the .NET 3.5 Service Pack 1, introduces some really big items like Entity Framework, and ADO.NET Data Services.

For those of you living under the covers, Entity Framework is big. It raises the abstraction level between the data mapping and the object model. Programmers can then code against object model level abstractions rather than lower level constructs. You should definitely check out Entity Framework if you are remotely interested in developing applications that have a fairly complex object model and a database.