This episode was a bit odd. With the core four it felt like it was packing too much storylines into it while with the rest of the cast it felt like it was underwritten. As others have pointed out, the whole robbery part felt completely forced. Really a robbery storyline either is a cliffhanger or is the major driving force of a storyline for an episode, it shouldn't be some random part. They had enough to go on with the dealing with Betty/Archie kiss and the divide over Hiram.
The problem with just throwing this in is that the time used for it could have been used to help flush out the Cheryl/Toni and/or Josie/Kevin storylines. Each of those storylines could have used at least one more scene.
Cheryl's mom really is the worst. It is interesting that Cheryl is very much a stereotypical bully, in that she is lashing out at others because she is basically being mentally abused in her home life.