I'm also happy to answer general questions about parallel linear algebra and to point people to the appropriate literature.
That's a shame, because having collections of useful tools like that makes it a lot easier to keep track of options.
With that said, the main advantage of the library is its high-level of software-engineering, which tends to encourage the rapid development of new features. It is actively used within a large number of research projects.
From my perspective, Elemental is primarily about human performance. That it scales to thousands of nodes of Blue Gene and achieves performance on par with (and in some cases significantly better than) ScaLAPACK is really icing on the cake. Granted, I really like scalability and performance, but I will not ruin my code in the name of these things.