Macaw doesn't strike me as anything like Fireworks, other than the fact it is a tool for people creating assets for the web. Fireworks's killer feature was that it merged both vector and bitmap creation tools. Fireworks was great but it was primarily focused on creating image assets that will be displayed on a web page. (The best tool for this nowadays imho is Sketch.)

Macaw is basically taking another stab at the Dreamweaver model. The major hurdle I see for it is that it seems to be a one-way street if you go by the demo. You can generate code from a Macaw project, but you can't just pop open your existing html/css and start working with it. The main asset you are working with is a mcw file.

For real-world work on serious projects, people in the trenches are going to manually hack on the CSS. They're also going to be generating HTML on the fly with code and will need templates to plug into their view system. The creators of Macaw seem like they know what they're doing but they need to have a story for how they fit into a real workflow before this makes sense. Their smart code generator looks like it will be great for getting a mockup together, but the killer app will be is if this tool can be used throughout the life of an app to iterate on its design.