I have already tried out the service. The editing is in WYSIWYG mode by default - and it looks quite nice. The web interface is almost as good as some WYSIWYG programs. For all you advanced users out there, there is also an option to edit the HTML of the site. It also have a 'Upload Stuff' feature that can be used to, eh..., upload stuff. I have not yet tried out all the features but I will try it as soon as I get some free time.
Be warned though - the site is in Beta - so expect many errors. I encountered some of these when I tried it out. Don't trust it with important data - there is a chance for data loss. Just make sure you have a backuped version on you local system and you should be fine.
Sreekanth, a colleague of mine have been playing around on this service much longer than me - he have already created a site that would pass of for a real site. Try it out - if you have a Gmail Id, you are already registered for the service.