Since Day One, I'm a fervent user of Firefox 3.0. Fast, simple, flexible : to me, FX3 is more powerful than Safari 3, and easier to use than Opera 9.5.
Firefox is therefore my default browser on my Macs and the PC. Each of them with the same setup, thanks to the Web 2.0. My favorites extensions : Feedly for reading my RSS feeds, Yoono for sharing stuff for myself between my computers, and to share things with the World too, and Piclens for pics & vids browsing and viewing.
Yesterday, the Mozilla Labs introduced a new add-on : Ubiquity. Read the description, watch the video, and install the first release. You'll discover a brand new way to deal with the Web. Absolutely stunning. Ubiquity might be the Web 3.0 (no typo ;-) for the rest of us.
We Mac users recently became used to hit the Space bar quite often - not to create a space between two words, but to read a document w/o opening the corresponding app. With Ubiquity, we're going to hit this Space bar even more often.
Ah, I forgot : for those of you who are still on IE, Mozilla Firefox is there.