It's an overall buff to ganking, as well as
and
since you can now both grab a buff and use your smite on a champion when ganking just after.
It's an overall buff to ganks, because they might well put you out of your jungle for more than 60 seconds.
So you can now, grab jungle camps and buffs, gank recall, and then go grab more camps, but you can grab both Krugs and Razors before going to push that mid tower down, you no longer have to chose between them.
IMO the 15sec CD on useage is a bit steep, but I guess it's to limit the amount of double-smites in teamfights or when fighting dragon/Baron.
It's just a shame that you don't start with 2 smites, that would have made the jungle a lot more forgiving for a lot of junglers.