I work for a government department, we use DW only for mockups, we use notepad for the live sites. Notepad certainly produces the cleaner code.
At home I use both. For my wifes business I use Dreamweaver, so I can easily make a change and she can view it as I do it. For my own site I use Komodo Edit (free editor).
Both have advantages and disadvantages, both also have a place in web design.
As far as purchasing DW, certainly, it is worth the inital outlay