huju: Exit polls have been used for over 50 years and have proved very accurate.
I am not so sure. As far as I understand, exit polls are re-weighted by the results of actual votes – and then they provide excellent insight in voters’ minds. This, of course, hinges on accuracy of the voting results. I am not sure whether unweighted exit polls are accurate (and this is possible to test given the known votes). It is also not clear how prevalence of pre-voting affects exit polls.