I just checked out Brimelow's video's on Catalyst + Builder, and played with the new beta's. It doesn't seem like you guys are doing enough clear thinking on how to simplify the tools, and steps, required to build great RIAs. Catalyst feels weird, disjointed, and yet another tool to learn that may or may not be worth the investment. The process for bringing custom interface elements into Flex still feels more convoluted than it could be.
I'd be happier to see Illustrator Builder. Illustrator with the ability to convert graphics into interface components, and a code panel. When you click an interface component it's document class is shown in the code panel. Other optional panels would include, a property/method panel, an import panel, a child panel. I don't mean to be a sour-sam but my initial impression, after getting some hands on use, isn't good. I think it's likely I may continue to stick with Flash + Eclipse.