You've got to stay on track with updates, which is not always obvious with the frequency of updates in Project Online!
Did you notice? No? Have a look to your project center ribbon...
Got it? You have 2 new check-boxes, rollups and Gantt Chart. Quite easy for the second one, you can hide or display the Gantt Chart. I guess the first use concerns portfolio views where Portfolio Managers want to focus on data more than on the Gantt aspect.
The second one can be interesting also. You can hide or display rollups while using grouping data in views. The objective might be to load faster views
This could propose this type of interesting portfolio views.