pjumbo - not trying to have a go at you or anything, but I would like to think that the bottom line on any flight, not just ETOPS, is having enough fuel to cover the worst-case scenario. The thing that makes ETOPs different from 3- or 4-engined long haul is precisely "system redundancy and all the other multitude of requirements".
767bill - the JAA, like the FAA, also publishes screeds and screeds of stuff on ETOPS - I don't have a reference off the top of my head, but if the FAA doc quoted above by hunter58 doesn't satisfy your curiosity then try the JAA's site.