The first post was far too well-written and articulate to be her own work, I wonder where she got it. There actually is a lot of truth in it, which is even more surprising.
Still, the biggest problem the USPS has isn't so much the union issues. Federal employee unions have very restricted bargaining rights, unlike State, municipal, education, and private sector unions...having worked in Federal labor law for many years, the unions are the least of a manager's problems after EEO complaints, Congressional inquiries, and just a natural disinclination to do the dirty work necessary to document enough misconduct or inefficiency to fire someone (Which is just as difficult whether the employee is union or nonunion).
No, the biggest problem the USPS has is the fact that Congress maintains a death grip on it that distorts its accounting and deprives it of the freedom to act in a rational businesslike way. Both the Congressional Ds and Rs are to blame because each has particular reasons keep it messed up. The actual agency is left in a situation where they are accountable for the results without being entrusted with the authority and responsibility to change them.