Yes, they were fun! . I imagine they have ditched them now because a) internet b) not v good to encourage all nighters and c) people avoiding the modules, although I specifically chose them (weirdo!). And maybe d - death by dangerous cycling.
Basically you cycled like a mad thing to the dept , got you a paper and then had to hand in your essay 8 or 72 hours later. If you lived off campus you usually used a friend's campus room otherwise the mad cycle back ate into your essay time.
Lots of people in the 72 hour one dossed about for about 60 hours and then suddenly panicked and made themselves ill filling the last 12 hours with non stop writing : it was essentially meant to be an essay per day.
I did get a first in one of those (the Romantics which I think was the 8 hour variety) so maybe the pressure suited me!