Well, I figured this day would come. My links to the older 3-panel style Salesforce docs for Apex, VF, SOQL, API, etc, now all redirect to the new "Atlas" style docs. For example, this: https://www.salesforce.com/us/developer/docs/apexcode/index_Left.htm now goes to https://developer.salesforce.com/docs; if you want the Apex docs you have to use https://developer.salesforce.com/docs/atlas.en-us.apexcode.meta/apexcode/.
I find the new docs unusable - every navigation click reloads the entire page (slowly), the navigation tree often collapses after navigation, and the nav is in the same panel as the content, so scrolling the content moves the navigation - a pain when you are trying to flip between a couple of pages of reference. Up until today, the old links continued to work. Anyone know of a way to access the older docs?