Attached is a document that lists all the bug fixes and enhancements (submitted via Esri Technical Support) that were addressed in Web AppBuilder for ArcGIS Developer Edition v2.9. Please be aware that the list includes issues addressed in the embedded version of Web AppBuilder in ArcGIS Online June update.
FYI: on Jan 17th, Gavin Rehkemper and David Martinez will present the following
Extending Web AppBuilder for ArcGIS
In this webinar, you will learn how to extend Web AppBuilder for your own custom workflows. We will dive into the Web AppBuilder framework to demonstrate how you can create your own widgets and design the look and feel of your app using a custom theme. We will also discuss patterns and techniques to streamline your Web AppBuilder development.
This is a great article on Linked In published by Ian Wint, GIS Manager for the City of Fort Lauderdale, FL. The article discusses how GIS technology was used by their Emergency Operations Center to prepare for and respond to Hurricane Irma. Web AppBuilder for ArcGIS and Story Map Apps were used to support their various app needs.