IGN.com loaded in 45 seconds over a 2 meg connection this morning, compared to 28 seconds in Chrome. Gamespot.com loaded in 27 seconds in Firefox 3.1, compared to 20 seconds in Chrome (the site doesn't have quite as much rich content today -- no sprawling ads). Disney.com (not one of my favorite sites but a good test of load speed) took 30 seconds to load in Firefox 3.1 and 25 seconds in Chrome.
The Firefox 3.1 beta includes a new feature for tab switching. It's kind of lame. When you press CTRL-Tab, you see large thumbnails of your tabs, but they look sort of munged. And how much tab switching do we really need? It's easier to just click the tab.
There's also support for CSS 2.1 and 3.0 properties, which is a little "heh" so far. I haven't noticed any major compatibility advantages, and -- in fact -- the 3.1 beta seemed to get confused by Disney.com.
The awesome bar -- which allows you to search through visited sites -- adds a few key commands for the true techies. You can restrict searches to only bookmarks by using *, or only search your history by using ^. LifeHacker goes into much greater detail on these minor syntax perks.
ReadWriteWeb has a good summary of the code enhancements. I'm not really jumping up and down about any of them. There's a new way for developers to access GPS data from mobile devices (using a geolocation API) for geo-location services. For example, a Web app could conceivably know that you are near a coffee shop with Wi-Fi and let you know the pricing options.