They position themselves as the Quark XPress of the web, and they're right to do that. With some help from the browser makers, they should be able to make simpler HTML do the same stuff. Writers So far no one has offered a writer's tool designed for web writing. Most page editors don't even have a spell-checker. There's room for lots of innovation here.
Text is more structured on the web.
So far the focus in webwriting tools has been on making HTML manageable, but these products are actually more useful to geeks. They're not really writing tools, just early releases in the small-site segment. In the future, HTML will not be an issue for writers. They won't write in HTML, they'll write in English, Spanish, French or Chinese. If you don't want a cookie-cutter website, you need an empowered geek to make text flow thru templates and scripts out to the site.