Google has been speaking very highly of the feature, while also making sure people know it's still a work in progress. Either way, it's already increasing the number of searches people perform on Google, according to the company. The Wall Street Journal ran an article after interviewing Google's Amit Singhal. Here's a snippet:
“Early indications are that people are interacting with it more, learning about more things…and doing more
On Tuesday Google spokesman Jason Freidenfelds said the company’s internal data continues to show people are “doing more searches as a result” of the revamp, though he and Singhal declined to share specific figures.
Google ran a doodle on its homepage this week celebrating the birthday of Fabergé Egg creator Peter Carl Fabergé. Despite an extensive and well-sourced Wikipedia entry on the man, Google did not display "knowledge panels" for him in its search results. This shows that Google has a lot of expansion to do on the Knowledge Graph, and it's interesting that they would highlight someone that they don't have knowledge panels for with a clickable doodle, which takes you straight to Google's search results for him.
If the Knowledge Graph continues to contribute to increased Google searches, that could do wonders for Google's search market share, and ultimately mean a lot more AdWords impressions. It will be interesting to see how the market share trends as the Knowledge Graph expands, not only to cover more topics, but to include more data sources.