I just hope this doesn't get raked over the coals by disappointed Fallout fans. It *appears* to have much more in common with Borderlands than Fallout. Obviously we don't have firm details yet, but from how it was described, it's not going to be open world in the Fallout sense. More in the Borderlands sense, eg large sprawling interconnected levels that are open within themselves, but it's not one big open sandbox. More like a bunch of smaller ones joined together. If you played Borderlands, you'll know what I mean.
Can't wait to see more details! I'm on board so far!