OK, so the new Mac OS restarts everything you had open when you shut down, plus some.
THIS. IS. THE. STUPIDEST. FEATURE. EVER. ADDED. TO. ANY. OPERATING. SYSTEM.
What it means is that every time you start up your system, to, say, send off an urgent e-mail, you have to wait for every single thing your were doing the last time the computer was on to re-start.
Including... oh say, that web site that hung the computer yesterday. That hang that was the very reason you shut the computer down.
That hang that will now hang your computer again before you get to send off that urgent e-mail.