I'm a big fan of Fire Fox, I've been using it since version 1. They are on the cutting edge of what a web browser can do. They had multiple tabs, and folders in your bookmark bar way before any else.
And they are aggressive about improving their product. Just check out some of the add- ons you can download and install to customize your web experience.
One of my recent add-ons is PicLens
Full-Screen, 3D -- PicLens transforms your browser into a visually stunning experience for enjoying online photos and videos.
This is a great add on for designers who are constantly using google image search or flickr looking for inspiration. PicLens also supports YouTube, so think floating video wall!