Out of the few songs I tried to play, IMN
is the only one that comes to my mind where Ryan really needed that low G (but i've read that most songs on Lost&Found need it). He uses it a few time to get the A# and to do some bend that would have been harder to do on the 1st few frets on the C string.
Other than that... well, like a low B in standard tuning, it is nice to be able to play some notes higher on the neck.
The cons? it isn't easy to get a good sounding low G string. You probably will need some custom set ($).
In fact you just made me want to try again that tuning
I have been using some DR DDT 135 to tune down to A and I wonder if they would handle such a low tuning