If you’re using Dreamweaver and don’t buy this, then stop doing Web design. Just stop. You’ll be doing the whole world an enormous favor.
Eric Meyer is the guy when it comes to CSS. He’s a wizard at it. He’s also a Web standards type of guy too — and you know how I love Web standards.
Heck, I hand-code my stuff and I’ll probably start using it (and Dreamweaver) just to off-load some of the routine stuff so I can get designs done faster.