Opportunity to shine, but expected to be Jack of all trades
Pros
Opportunities to impact business decisions and derive business value that will impact a lot of jobs in the field. I like the involvement with the business customers to come up with business rules, and then I get to put it to work. Choice of tech stacks and implementation is left largely to the discretion of the developers, so you have some opportunities to show your creativity, and in the process create a niche for yourself within your team.
Cons
It's a union position, so pay is non-negotiable and is not performance based. As a result, you have people that truly perform sub-par and are an ankle weight on the project - with little to no actions that you can take to correct the situation. Also, although the starting wage is quite respectable for a new grad out of college, it is largely agreed upon that the longer you stay with the US Postal Service, the less competitive their wages are for Developers. (Absolute Max you can make as a developer is currently $87,960 - no small peanuts, but imagine that this is after having approx 20 years experience. You could be making well over 6 figures elsewhere)