We're using it for creating reports for our web application, and I must say, its some powerful stuff.

The ability to create html,pdf,xml, or whatever, is awesome.

But the only real example I can give you is this:

We were creating a Rap Sheet, which a summary information page about a criminal. And of course, the boss wants a picture of the criminal on the report.

Only problem was, the pictures we save for criminals, we encrypt before we save them on the web server. So we couldn't simply throw an Image element on the report and display it, since it was encrypted.

But, in the RDL, you can define instances of custom code, which the report server will call, and we were able to add a Custom Assembly to the server bin directory, which the report server would call when it reached the Image element.

The custom assembly (a sql reporting services fancy name for your own class library), https to the web server, grabs the encrypted image, then runs the decryptor, returning an array of bytes to the Image element in the report.

After we had accomplished that feat, we were sold.