Pros
At it's best, Nielsen was a business where you could start out in ops, marketing, the field, technology, wherever, and learn/grow your way into a completely different part of the business. At one time, you could learn directly from the people who built the modern version of the business during the 70s, 80s, and 90s as they reached the end of their careers and worked to establish successors.
Cons
Private equity, abandonment of quality as a defining principle and marketplace differentiator. The old checks, balances, and quality measures have all been abandoned. The devolution has been slow but steady since the 2000s (see Dave Calhoun (GE, NBCU, Boeing) and Jack Welch evangelists brought less six sigma and more brute force offshoring/outsourcing to the business. Evergreen/Brookfield have only accelerated the inevitable dissolution/parting out of what was once a powerful, global business.