We mostly use and recommend Magnolia for enterprise clients who want a lean, easy to use platform for managing their content (not just on the web). However we do also use it internally for our own website as well.
It's not the only solution our clients use as everyone has different requirements. Why do we use it and recommend it to others when we do see a fit ? Quite simply, it's a well engineered product which has always been ultra reliable whenever we've deployed it to the dozens of clients who we've worked with it on. We don't like implementing solutions that we have to constantly prod and patch to keep working, and for us Magnolia saves us time, money and credibility. Our clients are always happy to use it because it is simple to use and takes minimal training.