Do keep in mind, it is still a beta (early beta) so some features will not work or not yet implemented (from the Flash builder). But do give it a try (there is always the Free plan) and let us know what you think, we really want to hear your feedback.
To create an app in the new builder, click Create more options:
Then check Open in new (beta) app builder option:
New builder welcome page:
Visual designer in the new builder:
Also, do keep in mind:
- Any already existing projects will only open in the current Flash builder.
- Any new projects, once created in the new builder, will only open in the new builder.