App Tabs in Firefox 4. That matches how I set up my operating system and browser. I think this will be a useful feature. The presentation of the new features in Firefox and getting people ready for them in this manner is very well done. Congrats to the Firefox team. Happy customer here :)
kodova : I don't know who came out with it first but Google is doing the same thing with Chrome and I think has has the feature in beta for a while now. They are also creating an web store to allow people to find web based applications.

http://blog.chromium.org/2010/05/chrome-web-store.html
Why ppl don't install Firefox. It is a sign of a mature organization that they do usability testing.
Interesting: "With the release today of Firefox 3.0.5, we're no longer displaying a EULA on install ... Instead, we'll be displaying an infobar that makes people aware of the about:rights text, which outlines how Firefox is licensed, the first time Firefox 3.0.5 is run."
Cam Riley: South Sea Republic. Freedom, liberty, equity and an Australian Republic.