Pros
Coworkers and lower level managers. The lower level managers had a good amount of latitude in giving hours, so they simply avoided giving time to lazy/unproductive people that made our lives difficult. Those of us who were not effectively fired were always very nice, tolerable people with lives outside work. My managers knew that I preferred stocking in the evening and working with the animals more than continuously trying to sell to cattle so they let me work when I wanted. It should go without saying, but I loved working with the animals. I got to hand-train a conure and raised litters of rodents.
Cons
The condition of the animals was very bad before I arrived. I kept things as clean as possible all the time (particularly the birds and rodents) but the employees that I replaced did not care enough to even try. On the one hand I loved working with the animals and wanted to ensure that their living conditions were good, but on the other hand I realized that I was in part supporting an organization that did not maximize the animals' welfare. I'm no PETA nut, but I have mixed feelings about the whole situation. Low pay. I worked hard and deserved more. My manager gave the pay raises that he was allowed to give. The company makes money by not paying the employees enough to make the job attractive on monetary terms alone and counting on people who just want to help animals.