The Hi-Fi CSS session was extremely nuts and bolts from four leading CSS practitioners. (Eric Meyer is here, too, in other CSS sessions.) Cascading Style Sheets lets you separate content from structure, meaning that you can avoid hard coding the appearance of a Web page. Rather, you tag elements of content and then use CSS style sheets to control their appearance.
Note that all five panelists were using Macs. But then correlate that with the fact that when Molly Holzschlag asked, the audience volunteered that most of them were coding Web pages in text editors, as were all of the panelists. (I use Movable Type for most of my Web sites now, so I use MT templates which aren't per se viewable in a Web design program. So I combine hand-coding of CSS with some visual previewing and templates.)
General notes: Make sure that the names you choose for CSS has a meaning, but note that function could change over time, thus naming something with a meaning related to appearance could make CSS less readable later. Terrible bugs in browsers means that CSS is ugly. Let's make CSS more like the beauty of nature over time. So occasionally we make CSS where it's not the perfect solution, but it's elegant. And, a nifty trick for doing double rollovers in which one rollover triggers another action elsewhere on the page using CSS (a:hover selector).
Malcolm Gladwell's keynote was very entertaining, drawn largely from his book, Blink, which I haven't read yet. It was a very interesting talk, though, and the main thrust is that people make very important decisions about life and death based on snap decisions that are provably inaccurate or wrong. But, at the same time, it's possibly to refine the information coming into a snap decision to improve the outcome of that decision. I'm a big fan of The Tipping Point, so will have to read Blink now. (Gladwell bon mot: I don't want my obit to read, "Malcom Gladwell, 87, author of The Tipping Point..." which is why he wrote a book he thinks has unrelated ideas in it.)
Dan Gillmor gave a talk that I've heard different renditions of from and about the ideas in We the Media. I like it as always, but don't have anything new to extract from it that Dan doesn't already say well on his own site and in the book.