Advantages: Divebombs, flutters, etc. All the cool tricks in the book. Even just some nice subtle accents. It stays in tune for years. Maybe not quite, but I tune mine maybe once a week.
Disadvantages: You’re more or less stuck in the tuning and string gauge it’s set up for. If you want to change tuning or change the string gauge from factory, you’ll have to do a lot of readjusting with springs and tension. You also can’t change tunings on the fly, and restringing is an afternoon project (not quite, I’ve got mine down to 45 mins, but it can feel like it.) Also, like Ed said, if one string suddenly changes tension drastically, the whole guitar is out of whack. So buy good strings.