If you're the sort of person who easily pauses a movie and never comes back to it, this one is a challenge.
The infamous pie scene IS pretentiously long, but if you stop watching within the first half hour you'll just have wasted your time. If you stick with it, it builds and builds and goes to unexpected places, and those first slow thirty minutes become an important piece of the whole.
The whole 'ghost as a guy under a sheet' gimmick quickly becomes crucial to the pathos because the ghost is human and feeling, but simultaneously alien and in many ways frightening. Not jump scare frighting, but "what if life is meaningless" frightening.
It's the sort of film that sticks in your head and you end up thinking about over and over again. It's an enriching experience and I'd really recommend it. It's art house as fuck, but then it knocks down the art house and rebuilds it again in a really cool way.
"Who are you waiting for?" "I don't remember." gave me the best chills.