I know it is not so nice to complain and bash a project when you don't contribute to it. And yes until now, I did not contributed to the KDE4 desktop as I wished. I compiled it regularly and used the libraries, but did not run the KDE4 desktop or KDE4 version of the applications except KDevelop and Quanta.
But as 4.0 is approaching, I decided that it is time to test, use, report bugs and even make fixes to it. I use KDE since a long time (~7 years), I think I always compiled from source, and for several years I compiled from CVS/Subversion regularly. I wasn't afraid to use the alpha/beta/whatever version as my daily desktop.
But with KDE4 somehow I feel lost. I tried a few days ago to start a KDE4 session. After getting through some issues that the libraries were not found unless LD_LIBRARY_PATH is modified (and knotify even with this setup has problem to find libkaudiodevicelist.so), I finally got it running. Well, it looks nice at first. So what to do there? I can start the KDE4 applications from the Run Command dialogbox. This dialog is a nice improvement over the old version, especially the autocompletion is handy.
In my version the menu was still missing, which isn't nice, but I don't care that much. What I care more is the speed, or to be exact, the lack of it. I blamed first the debug version of the libraries and the desktop, so I did a complete fresh build without debug information (a sidenote: my KDE3 is compiled WITH debug info and works fast enough). Sadly, it isn't faster. An example: right click on the desktop, and until the menu is shown, 3-4 seconds can pass. During this time Plasma and XOrg are heavily using the CPU. Moving around a window makes again ~58% CPU load (by kwin). Moving the mouse over the taskbar gives me 60% CPU usage by plasma AND 50% CPU usage by XOrg.
This slowness if everywhere on the desktop. I click somewhere and it takes some seconds until it reacts. The "natural" reaction is to click again, which makes things worse. What is the reason of this slowness, I don't know. But I am worried about it, because I have a fairy decent computer here, everything is fast except my video card: AMD Opteron 180 Dual Core (2.4Ghz), 2GB Dual Channel RAM, 7200RPM SATA HDD, Nvidia FX5500 card (with the binary drivers). The card isn't the state of the art one, but should be more than enough for desktop usage. I tried compiz with it, and it works OK. I can see the reaction lag with compiz as well (compared to the KDE3 version of kwin, which is lightning fast), but it is still quite usable.
I tried to remove kwin and use another window manager. This made at least the window operations faster, but the desktop was still slow.
That's about the speed.
Now about the usability side: I have no idea if what I tried is implemented at all or not, if there are plans to do them for the final release or not, but certainly I can say that as it is now, it is close to be unusable. There is the panel on the bottom with the taskbar and the clock. The taskbar let's say works, but I couldn't figure out what really a left/right click on an empty area of the taskbar does. It minimizes/restores the running applications, but I don't see the logic. I also don't know how to move around the taskbar on the panel. I don't know how to move the panel. It is possible to add new applets to the desktop, but I don't know how to move those applets to a panel. Moving them around on the screen is terribly slow.
There is also an Unknown Applet on my panel which "could not be created". I have no idea what it is or how it appeared there.
I also saw some bugs, like black boxes on top of windows appearing when you move a window over an applet, but this kind of issues are just simple bugs, acceptable at this stage of the development.
Unfortunately this experience can have only one outcome: I cannot use KDE4 as my daily desktop. Not even as a testing desktop.
So the solution is to test only the libraries and the applications. Luckily it is pretty easy to have a setup where you can run KDE4 applications under KDE3. Well, the first and one of the most important applications is Konqueror. I'm writing this blog from Konqueror4. Altough I feel a slowness here as well (when navigating through the menus, for example), this isn't a big issue, it is usable. I saw some rendering bugs, an ugly infinite loop when loading a certain page, but I saw similar issues with the old Konqui as well.
There is a problem with the editor area where I write the blog text (home bring to the beginning of the text, not the beginning of the line, mouse scrolling does not work) and the closing buttons on the tabs do not work, but again, in beta stage these are "normal" bugs.
For the applications the solution is to report the bugs or try to fix them. :) I will happily report them.
My conclusion: as it is now, the KDE4 desktop should not be released. Luckily we have some months left until the final release, so who knows, it might really be usable. I have more confidence in the base libraries and the applications. I think there only some polish is needed, in general they should be usable, but as I said, I didn't test many of them either. But what I started up for a quick test seemed to work.