According to the website you have to buy in advance now as they do background/security checks. On the website (at least it did a month back) it said that a photo ID is made for each visitor. and you have to provide a reason that you are visiting (eg job in the industry etc) tickets cover all 5 days but not the trade events whcih are separate.
Boeing 787 will be appearing but Boeing have not confirmed if it will open to the visitors or just on display.
6 (or 8 ?) years ago i went in with a friend's media pass. the airshow displays and the exhibited aircraft was cool, but the trade show was... only interesting to those more related to the profession!