If you hate being home and having time off, welcome.
Pros
The pay is pretty good, lets be real its pretty hard to get $19 a hour for unskilled repetitive manual labor position, where you don't even need a high school diploma. Not even the mighty military can do that. Plus your job security is pretty solid outside of your probation period because of the union. Once you make full time one of the best positions in the Postal Service. You can always pick up extra work.
Cons
For people looking for a stable schedule and benefits other than health insurance, look elsewhere. Since you are technically "part time" non career employees all those sweet federal benefits you hear about are not available to you such as, sick leave, pto, and access to FERS, also you will have to work most federal holidays without holiday pay, as that is not part of the current contract. Work life balance varies greatly depending on the size of the office you work at. Larger offices more likely to work a full time schedule and possibly up to 14+ days in a row without a day off. Smaller offices you may only work 1 day a week on your relief day. Lastly converting to a full time employee is based on seniority so you might be waiting 4+ years to become full time, also time spent as part time is just garbage time once you convert to full time, then the clock starts as when to retire.