There's nothing wrong with using Dreamweaver as a tool to help you visualize what you're putting together. But if you don't know how Dreamweaver's doing what it's doing to build your site, you're working with blinders on.
I personally loathe DW because of the grungy bloaty code it generates; to me it's like writing code with mittens on. If TextMate had a little preview pane to see your layout as you work, I'd be very happy indeed.
Me, I'm a Fireworks junkie anyway. Best webdesign program ever made as long as you don't use its code.