This is an excellent and much needed new development. Its just too much to manage otherwise, especially if you have more than one client or identity.
To help you quickly view all the accounts to which you access and manage, we are providing one easy-to-digest dashboard with your basic summary statistics for each advertising account. From this single view, you can easily navigate to a specific ads account, or sort the columns and determine how all of your accounts are performing. The dashboard will be visible when you log in to your Ads Manager.
via Facebook 1 | All Accounts Dashboard.