The Mist held my attention the whole time, and there was an interesting attempt to capture how the dymanics of a crowd can change when under duress.  But there were plenty of flaws.  One of my pet peeves in movies is people acting implausibly stupidly.  I've never been one to overestimate the ability of fundamentalist religious types to act logically - but in this movie, the religious folks acted so irrationally and so drone-like as to be amost offensive.  The director at least made an attempt to justify the more stupid actions - the otherwise smart and rational neighbor who wandered off into the mist in order to prove a point was bitter and felt isolated by the rest of the townspeople.   The religious "end of days" rhetoric didn't really spread until things got really bleak.  And so forth.  But I didn't think these justifications quite worked.  

With slightly better actors, The Mist might have been a really good movie.   It's watchable as it is however, but prepare yourself for one bummer of an ending.