I like ADAD tuning. Like everything, it has advantages and disadvantages.


Advantages:

Many tunes can be played in different octaves without having to learn two different fingering patterns. If a tune can be played on strings 1 & 2, it can be played an octave lower on strings 3 & 4 using the same fingerings. Since it's an open tuning, chording can be a matter of simple two-finger chords and one-finger barres (unless you're masochistic and just want to work out complicated finger-stretchers.) Since the tuning doesn't include the third as an open string, it's neither major nor minor so one can play major and minor tunes with the same ease. But the main advantage is just that it's so easy to play melodies in.

Disadvantages:

Use of a capo is pretty much a requirement unless one really likes playing in D all the time. On shorter scale-length instruments, capoing up to the fifth fret (to play in G) is as far is one can go before the tone changes to something more akin to a mandolin than a bouzouki. Medleys of tunes in different keys require moving the capo. (This problem can be alleviated to some extent by using multiple capos. For example, if a medley goes from a G tune to an Em tune one can have a capo already in place at the second fret to play in Em and just pop the one at the fifth fret off.)

By the way, if you really like playing in ADAD there is absolutely no law against tuning a mandolin the same way. Trust me, the mando police are a myth.