Extensions -- plugins that add specialized bits of functionality to a Linux desktop -- have helped many free software projects succeed, including Vim, LibreOffice, Firefox, and Amarok. Could they do the same for the often-beleaguered GNOME 3 release series?
The GNOME Shell Extensions site has been running for a little less than a year now. Technically, it's in beta, but, if my experience is any indication, the problems are few.
They are easily identified by the comments, and can generally be solved by finding the conflicting extension that needs to be turned off. In some cases, an error will even take you automatically to a troubleshooting page.
Some extensions may be available as packages in your distributions, but the majority of the over 250 currently available must be installed separately for each user account.
Using the site, you can install each extension to ./.local/share/gnome-shell/extension in the current account's home directory by toggling the On/Off button on its home page. You can disable extensions by toggling the extension to Off -- or, more conveniently by installing Extension List, which adds the same list to the overview page. You could also try GNOME Tweak Tool, which is in most distro's package repositories.
For some, this installation method may seem an invasion of privacy. However, the tradeoff is that it allows the GNOME project to track the popularity of extensions and make decisions based upon them. For instance, GNOME Board Member Andreas Nilsson tells me that the popularity of the Shutdown extension is partly responsible for Shutdown replacing Suspend as the default exit choice in the upcoming GNOME 3.6 release.
Scanning the available extensions, you soon find that they fall naturally into two categories: those that work with the design GNOME 3 release series, making at the most minor changes, and those that not only recreate the panel applets of GNOME 2, but attempt to convert GNOME 3 into something as close to GNOME 2 as possible.
Even if you are satisfied with the GNOME 3 release series, you may find some small things to change. For instance, if you do not use the accessibility tools yourself, you might want to install Remove Accessibility to remove them from the panel.
Or, if you regularly launch multiple applications, you can correct the overview's default behavior with the Persisting Overview extension, displaying the overview until you specifically move away from it.
If you want not to be distracted by notifications when you are working, you can install Distraction-Free to ensure that they only display in the overview and not in the main window. If you use Suspend or Hibernate, you might want to consider installing the Frippery Shutdown Menu or Alternative Status Menu to add those options to the menu.
For the most part, extensions that work within GNOME 3's workflow tend to be relatively cautious. However, in the next few years, this category will probably grow and become more imaginative as users become more familiar with the interface.
Meanwhile, nothing stops users from installing applet-like or GNOME 2-recreating icons as well, although the mixture of design philosophies might end up being jarring.
Part of the design of the GNOME 3 release series was to remove the clutter of applets from the panel in order to reduce the confusion of new users. However, perhaps a quarter of the extensions restore the clutter by offering the equivalent of the GNOME 2 applets.