On surgery atm: I go in for the ward round, take a history from someone interesting, then if nothing else is happening, go home (as early as 10ish sometimes). However, a lot of the time there is some teaching happening, and occasionally you have to go to theatre which could keep you there until 5 or so if you're unlucky. I'm probably fairly mid-range in terms of commitment - i know people that have only come in on 3 days of this 3 week placement.
I hear medicine is more intense with the attendance requirements (here at least).