KDE 4.9 is a mature release, so you wouldn't expect major renovations. However, to judge from the second release candidate (technically, the 4.8.97 release), that expectation is no more than half correct.
Yes, the release is full of the small refinements that characterize an incremental release. However, it also includes some more important features, most of them to do with Activities, as the development team continues its efforts to make the release series' most major innovation more appealing and useful to users.
Users wishing to try the release candidate can always compile from source, or check the development repositories of their distribution.
One of the easiest ways to test the release is to add the Project Neon repositories to an Ubuntu installation, then update the repository and install the project-neon-all package. Project Neon installs as a separate desktop that you can choose at login, and therefore doesn't overwrite any existing KDE installation with code still in development.
The small changes in the release candidate begin with KWin, KDE's standard window manager. For those who have poured over the settings of Desktop Effects in System Settings, trying to figure out whether an effect is working, the 4.9 release provides some relief by telling you when one doesn't load.
Other new window manager features include the addition of a desktop edge hot spot for displaying the different windows used by the current application, as well as numerous bug fixes for other effects.
At a time when GNOME and Ubuntu are moving away from traditional file management, KDE continues to fine-tune the Dolphin file manager. The latest release sees Dolphin allowing metadata to display beside icons, as well as renaming being done directly on the display pane, instead of in a dialog window that often obscures the item being worked upon.
Another basic part of the desktop, the Konsole terminal, is improved by the addition of the ability to drag a tab on to the desktop to open it in a separate window.
Desktop utilities also have their share of micro-improvements. For instance, the document viewer Okular gains the ability to print annotations, and is now aware of hyphens in its search functions.
KDEPim, the personal information engine, now has the ability to import filters, calendars, and address books and to do scheduled archiving of mail folders, while KDE games -- especially Kajongg, KPatience, and KSudoku -- each have numerous improvements listed in the release's Feature Plan.
Naturally, how much any one of these small changes matters depends on your work habits and preferred applications. Most are welcome, but not essential extensions of functionality. However, if these small changes have any unifying theme, it is making KDE behave more logically and usefully. Most users are likely to find something in these small changes that makes working in KDE just slightly easier.
One of the major features in the KDE 4 series is Activities, which are task-oriented virtual workspaces with a high degree of individual configuration. Past releases have seen KDE perfecting Activities and their interfaces, but the 4.9 release is particularly rich in refinements.
To start with, the interface for setting up Activities has been tidied, The horizontally scrolling display of all Activities remains the same, but the panes for individual Activities have been improved. The mini-icon of a wrench for editing settings is no longer half-hidden by the general icon for the Activity, making it easier to see and click.
In addition, the field for entering the Activity's name has been moved so that it is directly over the Apply and Cancel button when you click the wrench, making it easier to notice. The Activity name field has also lost the unresponsiveness that plagued it in earlier releases, and is far easier to type in.
The cumulative result of these interface changes is that Activities are far less awkward to set up than in current releases. There is still room for improvement -- in particular, the Create activity and Add widget buttons need to be moved from the right side of the scrolling window, where they can be overlooked -- but the changes in the release candidate are still a move in the right direction.