Pros :
It can look nice if done properly.
It increases the value of the property.
Good way to conceal unsightly pipes.
Good way to have diffused and recessed lighting.
Good way to hide sound and heat insulation.

Cons :
Cost, anything with the L Box will be expensive.
Pest. It is a haven for lizards and spiders.
Unlike a full plaster ceiling it has no fire retardant properties as the flame will go straight into the crevices.
It lowers the ceiling height.
Any water leaks will be costly to fix.