When I worked at Microsoft the guys in the Office team determined that most of the requested new features were already in the application, users just couldn't find them. So they undertook a wholesale reworking of the UI to make the bazillion application functions more "discoverable" while at the same time reducing the clutter that came from trying to make everything visible.
I see lenses as Sonar's solution to that problem. It gives you the ability to create highly focused, simplified views of the application based on what you need at any given point in your workflow. You may not need lenses, but I suspect that people who do need them need them badly.