RapidWeaver is a modal application. Either you're editing, or you're previewing, and things work very differently in each mode.
Rather than offer templates for you to edit like iWeb, RapidWeaver has a set of themes that you can apply to your pages. The difference is subtle but makes working in RapidWeaver very different from working in iWeb.
This time around, there's more flexibility and more chances for you to meddle directly with what's happening under the hood. You can edit raw HTML if you wish, add custom CSS files, mess about with metadata. Almost all of this happens in the Inspector palette.
The only controls visible in the main working window are modal ones; they switch you between edit and preview modes, open the Themes drawer, and publish your pages when you're done. Everything else is controlled in the Inspector, which has pros and cons.
On the plus side, squeezing all the detail into the Inspector means they can fit in a lot of stuff. You can do anything from change page title attributes, to set a file format and compression level (if appropriate) for images. The negative side is that it's easy to get lost in the Inspector; am I changing the title of just this page, or the whole site? Is this going to affect the navigation menu or not? How do I make that text box disappear?
Some of the things that are intuitive in iWeb might be more of a challenge in RapidWeaver. And because it uses themes, not templates, some aspects of content creation are hard to accomplish. For example, it's easy to drag an image into any styled text area, but impossible to make text wrap round it nicely.
But, the theme approach means that you can re-design an entire site, one comprising hundreds of pages, with a single click in the Themes drawer. The built-in themes are adequate, but there are plenty of third-party themes available at fairly low cost. You could spend a lot of time trying out lots of themes.
And that's one of the most appealing things about RapidWeaver, and why its name is so apt. Having started off with some basic content, you can build something and try it out in all manner of different designs in just a few minutes. The preview mode is very impressive in this respect.
But edit mode is less so. Partly because editing a page takes you into something that looks nothing like that page; you're editing in a form field, and your changes will be reflected once you return to preview mode. It's a mental leap from one to the other that not all users will be comfortable with.
If you can get comfortable with it, though, you'll enjoy it. The weblogging interface is nicely made, works faster than iWeb, and is easier to get your head around than Sandvox. It offers built-in categories, and podcast support, and can save items as drafts.
RapidWeaver lives up to its name. It's rapid. Building a basic website that includes a photo album, well-featured weblog and sundry text pages takes just a few minutes. Having entered all your content, it's quite fun to flick through the various themes and see which one best suits your needs.
It also benefits from being a 3.x version (as of the time of writing, 3.2.1). Many of iWeb's drawbacks are the kind of thing you'd expect to be fixed in future releases, but RapidWeaver's already been through that and its relative maturity is a big attraction.