For the most part the Odoo 11 upgrade was focused primarily on improving Odoo's underlying architecture. Instead of using Python 2.7, Odoo now uses Python 3.5. The improved design in Odoo 11 allows many operations to run up to 3x faster. This means that there are not all that many differences between Odoo 10 and Odoo 11 from a functional standpoint. Still there are a few welcome improvements that make the user experience more enjoyable.
Odoo 11 now features a new activities system that is integrated with Odoo's applications, VoIP, calendar and notes. Clicking on a small icon on the menu bar will display the current activities. Here is an example of what a Lead/Opportunity activity looks like in Odoo 11.
In Sales Management and CRM, Odoo 11 provides small interface enhancements, improving the user experience.