The flexibility of having multiple frontends or interfaces for my clients as well as being able to use it in an intranet environment is what I love best about Typo 3! It allows me, among other things, access control over certain pages within our Intranets which are not accessible by all users (especially those with less permissions).
Also we can easily manage different versions/revisions without any problems at this time - great software that meets most requirements very effectively! Nothing so far but there's always room for improvement :-D We have used typographic solutions from previous years now replaced completely since then; however still using some features like content management systems etc., they were too costly compared otherwise than others available outthere ;-).