I've used Fireworks a little to make template pages. How I use it is to create what is in effect a blank page, with menus, icons, roll over buttons etc. All that's missing is the actual content.
Then I slice the whole page up into components. If you are making mouse overs you can create them all in fireworks in their various states (over, hover etc). Then I bring it all into Dreamweaver and start working on the rest of the site and adding content or various images.
I probably have only used a fraction of it's capabilities but I imagine that if Fireworks could be used to create a full website then why would Macromedia bother making Dreamweaver! ;-)