* tabs will have close buttons
* the search box will resize when the windows resizes
* you'll search Google and Yahoo using inline suggestions from the search box
* Bon Echo will allow you to subscribe to feeds using a desktop feed reader (like NewsGator) or a web feed aggregation service (like Bloglines)* automatic spell-checking for multiline text boxes (useful when you post comments on blogs, it works similar to Microsoft Word's spell-checking)
* session restore (if Firefox crashes, it will ask if you would like to restore your previous session next time you load it)
* when you bookmark a site, you can select a microsummary. Microsummaries are small descriptions for web pages provided by third-party sites, for example instead of seeing "BBC - homepage - Home of the BBC on the Internet", which is the title of bbc.co.uk, you could view the latest news "BBC - US releases 9/11 Pentagon video".
* Safe Browsing will alert if you visit a site that uses phishing or spyware.
* Why Bon Echo? It's the name of a public park located in Ontario, Canada and it means "good echo" - Firefox 2 tries to improve Firefox 1.
Related:
You can test Bon Echo Alpha 3
Reduce memory usage in Firefox
Opera 9 - Discover a new world