I haven’t played too much with this tool yet and it is still in beta so it’s hard to be too definitive with any opinions right now but there are some things I can say about it.
As a tool for creating prototypes and demos, I think it has a lot of promise. It doesn’t seem to take too long to create something that will give you an idea of the user experience you’re developing.
To use it for full on development projects, it has a few drawbacks. Not all components have a Spark version yet and it won’t do round-trips right now so if you try and take a project you went to FlashBuilder with back into Catalyst, it complains. It’s still beta and from Adobe’s marketing material, it seems like they intend to have all that working at some point so those may be moot points later. A bigger potential problem in my view is how do you deal with an existing code base of lovingly crafted custom Flex4 components? If your designer uses Catalyst, it will be pumping out nicely skinned standard components and as a developer, you’re going to have to tease all of those out and replace them with your custom work where necessary. It’s going to get tough if you’ve got skinning involved in those components too. You’re also going to get one big monolithic app that probably doesn’t match up too well with any design patterns.
This is not to say that with planning and careful consideration of what you’re doing, you couldn’t make it work but for bigger apps it’s not going to be a trivial task to take something from Catalyst and make it work effectively.
I think if you were to use it to create the starting point for your reusable components and then still continue to do your main construction within Flasbuilder, you’re probably going to get the best results.
I’ll be interested to see if I can find anything on using it for larger projects and see what people come up with.