Hardest part of the job- it can be very stressful, and no one cares that you're stressed. Routinely, you have to turn away and dent people who need help and that can be difficult for anyone who has a heart, Very often, it seems like management doesn't care to help with any questions you have, isn't around to help, is annoyed that you're asking for help, or doesn't know how to help.
Most enjoyable part of the job is the interaction with the nicer customers. Seeing and conversing with the same smiling people on an almost daily basis, and you become as much a part of their daily routine as they do of yours, hopefully in a good way. Some days I would be feeling down and then see or talk to some of our regulars and feel an instant moral boost.