It's easy to underestimate the importance of this recognition for Acquia, and by extension for Drupal. If you want to find a good coffee place, you use Yelp. If you want to find a nice hotel in New York, you use TripAdvisor. Similarly, if a CIO wants to spend $250,000 or more on enterprise software, they consult an analyst firm like Gartner. So think of Gartner as "Yelp for the enterprise".
Many companies create their technology shortlist based on the leader quadrant. That means that Drupal has not been considered as an option for hundreds of evaluations for large projects that have taken place in the past couple of years. Being named a leader alongside companies like Adobe, HP, IBM, Oracle, and Sitecore will encourage more organizations to evaluate Drupal. More organizations evaluating Drupal should benefit the Drupal ecosystem and the development of Drupal.