Thanks for the quick reply! Understand that I have not bought it yet, I'm trying to clear up those questions. I am pretty capable at Dreamweaver and using extensions, but not experienced at all with CSS, I only have Joomla experience to compare this to.

Doug -- Site Sculptor is not a full-blown CMS system like Joomla. It permits a user to easily edit content on existing pages -- that said, it does not permit the wide range of site content creation provided by Joomla.
Think of SS as an initial site styling/page/navigation creator that provides pages capable of having their content updated.
How much do I have to go through to create a new page? A client cannot create a new page for his site through CMS? 
You as the Site developer can easily create new pages using the template created by SS. A "user" cannot, unless they also have access to DW and the page template file.
Another question: Can I add other extensions (for example, DWUser's XML Flash slideshow) to a page? If so, can I edit the XML Flash slideshow after it's been finished? 
If it's just content I see no reason why not.
Would you say that this extension is comparable at all to Joomla? 
In a word, no.
Sorry about all of the questions, I'm trying to figure out if this is a "real" CMS, or a limited version, and if using it will create restrictions rather than add usability. Believe me, I am hoping that I will get answers that will allow us to buy this extension. 
Hope this helps. . .
Mike


