You can now watch the full episode online at the PBS website, which I did tonight. Overall a good show though I too think they could have done more on the issue of how people respond to warnings.
Can't add much else, except to play nitpicker and point out a couple of gaffes, goofs or whatever you want to call them:
1. At 2:45 into the show, a shot meant to portray a residential street in Joplin just before the tornado hit ("5:30 p.m. It's just another Sunday evening, and then....") shows bright sunshine and clear skies (!)
2. Around the 32:00 mark, as Tim Marshall explains the convergence of winds, etc. that led to the Joplin tornado, the map over which he is standing has Missouri on the left and Kansas on the right! This had me baffled for a few seconds until I realized the viewer's perspective was facing south and looking at the map "upside down." Perhaps they could have set up this shot a little bit better to avoid confusion?