Although it is hugely customisable, it works fantastically with the default settings. It functions either as a stand-alone tool or, most usefully, integrated into Visual Studio with an extension. Analysis is super-fast and does not hinder development or make VS sluggish.

I love NDepend's visualizations. Specifically, their tree map visualization helps me pinpoint code quality issues or test coverage weaknesses. This is critical for communicating technical debt to management and getting buy-in for changes that need to happen. Additionally, the newer code visualization features are wonderful and something I leave open as a sort of map of my code, even when I'm not actively using NDepend's code smells tracking features, this navigation pane helps me quickly visualize the context of my current code within a larger application.

Easiness to integrate with current .NET solutions.