If you are looking to spit out a website using baked templates provided by WA Design Extender. Here are the Advantages.
1. CMS Builder, Menu Writer, Frame Builder, etc is implemented when utilizing Site Scultor to build your pages. This means that the moment you've upload everything. CMS Builder is ready and every page is already connected to the builder. So it is a matter of assigin a username and password for you and your client and letting your client import the information from there. Your almost practically done. (exception? You'll have to build the contact page from scratch...)
2. Everything is combined into on .mxp file so you won't have to install numerous exchange files to complish the same task.
Disadvantages (Based on what I've seen so far using it).
1. When publishing your site from Site Sculptor on to the web, the index.php (not in the admin folder, becomes rewritten and aimed at the CMS Builder index.php. Whic is the login page or CMS Builder Setup page. (to correct this, make sure that you have a index.html or index.php in your backup folder and use your homepage template to "Apply Template to Page" for your index.php file (that has been re-written).
2. There is no documentation on best practices when importing a complete website compressed in a zip file into Site Sculptor when Implementing a custom site design. My guess is to take a working site (complete with framework builder, site builder, css menu writer, etc) zip it and install it. If working on this write now so I'll have something solid to report.
3. if you are a web designer, and you are looking for an easy way to push your design without the need to script, this will not work. You will need to design you website, build it in either html, or php. Then your will need to implement it in Site Sculptor for replication (for multiple clients). Again, make sure that you utilize the extension before importing... It's better to be safe than sorry.
4. The CSS Menu Writer is MANDITORY, and I hate using it. I would like to make my own menu out side of the extension, if it works well, I'll implement it in CSS Menu Writer later.
These are my advantages and disadvantages... I don't consider myself to be a pro, but for the sake of thinking of beginners. This solutions, like other extensions WA needs a little more detail in the documentation. So, for me, I'm spending time understand in plugin to become comfortable, instead being comfortable wit it's features and building websites.
Again this is just me and my experiences... To each their own.