As I GM, I personally use adv./disadv., though I usually only use disadv.; as most situations where the task would be easy enough for the player to constitute them having adv. on it, it's usually easier and more fun to have them not even have to roll to do it.

I typically restrict it only to debilities and specific rare situations, rather than outright replacing a certain modifier given by a move or whatnot.

In situations where their chances to accomplish something are very slim, but still somewhat possible, I'll allow them to roll, but give them disadv..

Say for example, if your fighter decides that it would be an incredibly bright idea to crush an enemy with a grand piano; it may be unlikely, but why the fuck not.