The System Settings window has received almost as much attention. At the possible cost of confusing users, some functions have been promoted to top level items, and others have been renamed. The Advanced tab, a dumping ground for miscellaneous configuration options, has been eliminated as well.
Unfortunately, the System Settings window changes are not always improvements. Some of the renaming, such as the replacement of the Advanced tab with the vague Lost and Found, are vague and likely to be confusing, especially to non-developers. At least one other -- Application and System Notification -- is verbose and conceals the function alphabetically from those used to looking for Notifications. But the trend is toward more organization, and perhaps such deficiencies can be corrected in another release.
However, the greatest interface changes center around Activities. Introduced in the KDE 4 series, Activities are an enhanced version of virtual workspaces, and are intended to offer separate desktops for different activities or locations -- for instance, you could have one Activity for graphics and one for online communication, or one for home and one for the office, each with its own set of icons and other options.
In previous KDE releases, unless you knew the keyboard shortcuts, you managed Activities with a zoom view, zooming out to select an Activity, then in on the one you chose. This arrangement had the disadvantage of making the very existence of Activities easy to forget. Even more importantly, it was awkward to use, not only leaving new users to wonder what had happened to their desktop, but also hiding some of the controls if you set up more than three or four activities. Nor could you easily view larger numbers of Activities at the same time.
Now, in KDE 4.5, Activities are managed in a horizontally scrolling bar, much as possible widgets are. They are also easier to set up, with a new Activity menu offering the options to clone the current Activity, add a Folder View with a unique set of icons, or a general desktop without icons.
You may still want to configure new Activities with different wallpapers, but the new interface is both easier and quicker to use, and should lead many users to discover Activities for the first time.
The KDE 4 series could still use some polish here and there. However, for the most part, KDE 4.5 marks the end of the development cycle that began two and a half years ago with the release of KDE 4. Most of the issues people initially raised about the KDE 4 series -- instability, a lack of configuration options, the slow speed -- have now been addressed, and at best only minor tinkering seems needed.
The question arises, then: What happens now? Perhaps KDE 4.6 will be another round of small but welcome enhancements, but after that? Will KDE settle down to incremental releases? Or will a new vision of what the desktop might become lead to another series of major changes?
Either way, seeing what has been realized in KDE 4.5 emphasizes what is often missed in the controversy generated by the KDE 4 series. Regardless of what you think of the KDE 4 series, it has been an ambitious attempt to move the desktop forward -- an effort unparalleled anywhere else in computing. The verdict on that attempt may still be out, but seeing it mature in 4.5 only emphasizes just how unusual the entire KDE 4 experience has been.
If the 4.5 release really does mark the end of an era, then I admit that as both a reviewer and a user, I will be sorry to see it go. I haven't always agreed with what KDE has been doing in its recent releases, yet watching efforts to do something new is always exciting. If KDE does settle down to incremental releases, it might be inevitable -- but it will also be disappointing.