The people and how hard they actually work. Being expected to work with multiple customers at the same time.
The way management treats people make it negative. They believe in the rule of "punish all when one transgresses" against their dictates.
When you can get in trouble at any moment for not doing what they think you should be it makes it miserable.
It would be nice if they did not play favorites. You pretty much know who is going to get the promotion or recognition. They only value a few of their employees - or favorites. It tends to be the younger generation getting raises and promotions.