There is no exit door in front of the forward main deck (Zone A) cabin in the 747. It's the only type that I can think of where this the case.
Whereas I don't habitually check for life vests on boarding I do pay attention during the safety briefing. I used to think that the life vests were there more as a comfort for the non-swimmers as in practice they were never likely to be used given that the likelihood of a jet aircraft making a survivable landing on open water was debatable.
Moving on, when I was growing up one of our friends survived a major incident (East African Airways VC-10 crash at Addis - similar to the SIA incident at Taipei). By far the biggest impression that made on me was to remain sensibly dressed for take-off. Rather like the poster before, I keep my shoes on and remain dressed with all the essential paperwork/credit cards/keys close at hand or in a pocket until we are safely off the ground. Having everything ready to go means that you don't even have to think about a bag or looking for stuff should you need to evacuate. Exiting a plane in your flight socks or bare feet and running across broken glass/metal debris/spilt chemicals/burning fuel isn't for me and doing the post-crash debrief in your flightsuit strikes me as wrong too.