We're three episode into Jericho now, so time to pass judgement. So far, we're pretty sure about what kind of catastrophe has occurred and how widespread it might be and it doesn't sound good. We've also had to deal with the possibilities of fallout, looting and other post-apocalyptic calamities.
The fact this isn't a small-scale disaster is the redeeming quality of the show, which maintains a certain bleakness as a result. Since we don't know exactly what (or who) has caused the disaster, there's still an element of mystery to keep us going.
That's good, because the town is populated by normal (for which read “dramatically bland”) people for the most part, so their stories aren't actually that interesting. Only Lennie James and Skeet Urich's characters have the slightest depth to them. Maybe the other characters will acquire some kind of charisma later on, with the plot keeping us watching until then.
So an ambivalent thumbs up. I might keep watching. I might not. Everyone else: try it if you want but don't expect something wonderful just yet.