In all this, it's easy to forget the pieces of the puzzle that were originally planned for inclusion in Firefox 4 but are as yet not mature enough to be included this cycle. For example, there were originally plans to revamp the download manager so large numbers of downloads are more manageable.
That just means these features will likely be part of the plan for next release.
Download manager improvements - There was supposed to be a revamp to the download manager but since we're already in Feature Freeze, that means it's been deferred to a later release. The downside is that download status and management will be a bit less "accessible" since Beta 7 saw the removal of the status bar. Having no status bar just means the user has to open up the download manager window to check overall download progress.
Firefox button on Linux - The Windows version of Firefox 4 has had the Firefox button for some time now, but even Beta 7 didn't see it make an appearance in the Linux version. There's the general impression that Linux GUI toolkits aren't as easily customised as their Windows equivalents and this means we won't be seeing the Firefox button just yet.
Home Tab - App tabs made it but the permanent tab known as Home Tab hasn't made an appearance. I think it's safe to say it's not making it into Firefox 4. Remember the Home Tab Challenge? Hopefully that bears fruit.
Notification improvements - There was supposed to be improvements to the way the browser displays notifications but (so far) there doesn't seem to be any noticeable changes to the way Firefox is notifying the user of what's happening to their browser.
Firefox is a major overhaul of the browser. There's no doubt about that. There's just some interesting changes that were planned that didn't make it, as is always the case with software projects. In particular, notification and download manager improvements could have made the browsing experience so much better.
Installing Firefox 4 pre-Beta 8 on Ubuntu 10.10
Firefox 4 Beta 7 release