I do all of my XHTML/CSS in Dreamweaver although for quick mods I usually use Notepad++ because it's not nearly as heavy.
I use Dreamweaver for the following reasons:
- Decent Design Preview
- Code completion
- Great CSS integration
- Tabs (Stupid I know)
- Easy interface
Plus now that it's an Adobe product, I expect they'll start integrations with Photoshop (ie - in Flash you can now import a layered PSD).
Best Regards,
Patrick