From the developer's viewpoint, KDE's division of everything into separate modules makes for flexibility and easy of coding. But if you have any trouble setting up personal information, good luck using Akonadi to correct them. Akonadi is not only seriously under-documented, but is full of tools that give you plenty of information, but few indicators of how to act upon it.
First, there is the multi-tabbed Akonadi console, full of information that is either heavily abbreviated or invisible with dragging column rows open. The purpose of many of the tabs is further obscured by the fact that they are empty, and there is no indicator of where to start. The first tab might seem a logical place, but do you need to add something? Or can you jump right in and configure or synchronize whatever you're dealing with?
Then there is the Akonadi Configuration window, which seems to repeat some but not all of the console's contents. At first, it seems easier for setting up resources (even if you are not sure what you are setting up).
The best thing about Mate is that, if you're an experienced Linux user, you've seen it all before. Mate is a fork of the GNOME 2 code, and its developers have worked hard to reproduce most of GNOME 2's features.
True, differences exist. Instead of GNOME 2's cascading menus, Mate has a single window menu. Nor does Mate use GNOME 2's long-familiar trio of menus, Applications, Places and Systems. However, in general, any user of GNOME 2 should be at home almost immediately.
Mate's worst feature is the same as its best. Its resemblance to GNOME 2 is comforting, but also means that Mate consists of code that is not only aging, but threatening to become obsolete.
Average users don't see the code directly, of course. But the effort to update it takes up a good portion of Mate's development time. Add the ongoing cloning effort, and Mate sometimes, too, lacks innovation. No doubt that is part of Mate's appeal to refugees from Unity and GNOME, but if it sometimes feels comforting in its familiarity, at other times it can feel old-fashioned and as though it is spending too much time maintaining the basics.
Unity, Ubuntu's default interface, include many elements that prove that design theory is only as good as the assumptions you put into them. But one feature that Unity has got elegantly right is its launcher and its economical use of space.
To start with, Unity's launcher was the first recognition that modern screens have more horizontal space than vertical. Admittedly, the idea of placing basic tools on the left edge of the screen takes some getting used to, but, then, so did placing the main menu on the bottom left.
Another economical feature are the indicators for open and active applications. Instead of a bulky taskbar, the launcher simply uses a triangle on the left for open apps, and one on the right for the current app.
The launcher also includes a widget that stacks the apps at the bottom, making them still visible -- if only barely -- and easily retrievable. The launcher does scroll smoothly, but this feature provides a complete view of the launcher that makes searching for an icon much easier.