I work as a graphic designer in print but still need to design and publish the occasional website. I know my way around HTML and Dreamweaver but I have to say that I love working in iWeb.
While not suitable for most professional projects, it is good for creating mockups and "quick-and-dirty" websites.
The genius of this application lies in its simplicity. I find myself concentrating purely on the design and not getting caught up in the technical details. Once I've established the look I go back over the website and adjust things so that I get the results I'm looking for.
It's ease of use, including drag-and-drop and automatic guides, make the process of creating websites more like fun and less like work.
That said, it has a lot of shortcomings which keep it from becoming a top-notch web design app.
I'm disappointed that Apple seems to have abandoned iWeb. With some work it could be great.