•A Visual Designer
•Integration with Adobe Tools
InfoQ had a small Q&A with Huw Collingbourne from SapphireSteel Software, the creators of Amethyst:
The Professional edition has a full visual drag-and-drop designer for Flex 3, 4 and AIR. It has all the same refactoring options as C# plus one extra (move a class to a new package). It has full IntelliSense. It has our own debugger (the 'Amethyst Cylon' debugger) which integrates completely with Visual Studio and also does multi-process debugging to let people step through the code of multiple SWFs simultaneously. It is, in fact, a complete design-edit-debug and run IDE for the Flash Platform.
You can use Visual Studio to create and manage their software development projects. Microsoft has provided several ways to customize and extend Visual Studio to automate tasks or add features. You can create Visual Studio extensions for your own use or for distribution to other users.The following are some of the ways in which you can extend Visual Studio:
Add commands, windows, and other features to the IDE.
Extend the Visual Studio editor.
Enable support for a new language.
Extend data designer functionality to external data sources.
Add your own project-type templates.
Integrate custom source control.
Customize the Visual Studio debugger or create your own.
Create and manage your team test suites.