Pros
As a giant, PE-owned firm, while several are out-of-reach, there are many resources at hand, if you know where to find them. While not as esteemed as Marsh, Aon, Gallagher or Lockton, USI is a huge broker so there is some brand recognition in the market.
Cons
Abysmal culture, so very corporate, hardly any ethnic diversity. If you look at the leadership across the entire company, you'll find that most are white, and the majority in senior positions are male (Look on LinkedIn). USI is a case study of a huge company caring far more about revenue, gobbling up acquisitions left and right, and collecting contingent commissions from the insurers with whom they work (a huge no-no in the world of insurance) than their clients or employees. Above all else, there are zero ethical standards. The brokers and office leaders are wholesale unethical. Its really a downer to work for a company like this. Finally, it was never fun to go to work.