I'd probably also add: easy to build/deploy here.

The world needs better compiler tools, tools which are built as libraries. This design point allows reuse of the tools in new and novel ways. However, building the tools as libraries isn't enough: they must have clean APIs, be as decoupled from each other as possible, and be easy to modify/extend. This requires clean layering, decent design, and avoiding tying the libraries to a specific use. Oh yeah, did I mention that we want the resultant libraries to be as fast as possible? :)

• Chris Lattner (2007). Source: Original Clang README

But the irony, though, lol...