Dreamweaver is just a glorified code editor with auto-complete, the ability to connect to FTP and upload your work within the program, and a unique "design view" which lets you move coded objects around with your mouse and also give you a visual representation of what your work looks like without opening a full browser.
The problems are 1) The design view isn't the view that any of the major browsers see. That gives you a website that won't look like what you see no matter what browser you use. 2) Designing the site in design view gives you semantically incorrect, bloated code. 3) You're spending $400 for a text editor you can buy for under $50, or get for free. (The FTP part is also free - Filezilla.)