Pros
The Union sets rules that keep corporate/management from outright abusing their employees. We also get health benefits. A lot of co-workers make great friends and become "part of your family," in a way.
Cons
We work way too hard for too little pay. Managers frequently give terrible schedules, either cutting everyone's hours or flipping people's daily hours around so they have to keep changing their sleep schedule multiple times a week. Technology is outdated and frequently breaks or glitches, causing stress for both employees and customers. Safeway keeps pushing the whole "world class service" but makes it difficult for employees to deliver when there aren't enough people scheduled and all the customers are yelling at us because they have to wait in line. If customers become verbally abusive, management often solves the problem by giving them free stuff (and occasionally berating the employees). We are often given conflicting orders and get chewed out by someone no matter what we do. Morale is low and people frequently call in sick or quit.