I'm really glad to see all this innovation in WYSIWYG web editing software, and from my experience, Sandvox from Karelia Software is poised to lead the pack. Yes, I've been going on about how excited I am about the iWeb 1.1 update, but after playing with Sandvox's beta editions, I'm going to give this official 1.0 release a good run-through, as it offers quite a bit of power and some nice tricks that other products like RapidWeaver and iWeb can't claim.
The feature that impresses me the most about Sandvox is their innovative "Pagelets" feature. Pagelets are small chunks of rich content that you can simply drag and drop around your site's theme. Don't like where your blogroll is? Just drag its pagelet somewhere else. Pagelets in the pro version can also allow you to insert your own HTML and even PHP code into any portion of your site or sidebar. Speaking of site themes: Sandvox's are stellar, and a bit more creative than iWeb's. Sandvox comes with two dozen themes, with more available.
Sandvox also does a lot of the, dare I say, 'standard' WYSIWYG web design-ish stuff that I've come to expect on the Apple platform. You can drag your audio podcasts into a Sandvox site and get them submitted to the iTMS, as well as drag images from iPhoto, etc.
Overall, despite lightning striking twice for Karelia Software, Sandvox looks like a solid product that presents a strong array of features for the WYSIWYG designer that demands a little more from their web design app.