Our world is conducting ETOPS operations for about 40 years now and there was no single accident caused by this so far. It may happen one day but if you take into account how many flight hours were logged in during those 40 years, it leaves no space to doubt regarding safety angle. One of US majors did even overshoot the max diversion time due to the headwinds over mid Pacific many years ago, flying over 3 hours on one engine before landing on Hawaii. What else is need to be discussed here?
ps and no, Air Transat Azores glider does not count in here, with the same circumstances applied, it would be the same outcome with 747 or 340