Me, Sébastien Laoût, is returning back from Linux to Windows.
Several people were surprised (I understand!) and asked me the reasons, given that I was an active KDE developer (making BasKet Note Pads and Kirocker Music Display).
Here they are.

The only reason I used Linux was for KDE.
I love this desktop, the powerful yet very user-friendly KDE applications, the amazing Qt and KDElibs programming frameworks...
The framework is very easy to use, and allows developers to do very powerful things and have a HIG-complient standard interface effortless.

The problem is: to run KDE, we need to use Linux.
Don't get me wrong, Linux is a very nice piece of software, I loved reading a book about how it is implemented internally... but that was just "to know how works an OS", I don't want to code for the Linux kernel. And I'm not a system nor network administrator. I want my system to work, out of the box. I don't want to have to understand every piece of technology and hack them to make the computer just work.

Linux hardware support is not enough for me. It supports my hardware, but not fully, not all features.
I wasn't using WiFi (and I need WPA with that) because it wasn't working on Linux.
Sure, I could have searched internet for hacks to make WiFi working on my Linux, emulate Windows drivers, and whatnot. I've already done that for my previous computer, losing days searchings and trying... without success.
My Dual-Core computer was useless: only one core was used. And the desktop felt very slow.
Sure, I could have compiled my own Linux kernel to enable multi-core. But that would mean search the internet for how to compile the kernel, how to enable dual-core, how to do it without breaking anything...
As I said, I'm not a system administrator, I buy a computer, it must work smoothly out of the box.

But why did I switched back to Windows now?

Recently, I upgraded to the latest KUbuntu.
My previous dist-upgrades were not very fruitfull but the system still worked after.
I had to ask a friend to make all my previous dist-upgrade, and had to live with a broken package always wanting to be updated but that would never success to update...

But this time, the upgrade has been different:
- The CD-Rom is physically polled every two seconds, so it makes an horrible constant noise.
- The CPU is now always used at 100% by udev, watershed, and evms_activate processes.
- It seems like udev and fuse are both trying to manage storages, but none of them success. So I have no access to my Windows partition, no external USB hard drive access, I cannot sync my iPod music...
- The volumeUp/Down/Mute buttons and LED are not working anymore: the PCM channel now became the master channel for no reason, and the old master channel is now useless.
- Once in a while, the system says the battery isn't present anymore, and the battery is back a few seconds later.
- At every computer startup and shutdown, I get two screens of error messages and adds to the 10 error messages I got for a long time when starting Linux. The errors are not disturbing, but it's not what I call "a seamless working" nor "the system is completely controling the hardware in a clean way". At school we all use our notebook, I'm with Windows people and I'm always ashamed when such messages occurs.

Did anyone unlocked its iPhone and upgraded the firmware to see that the iPhone became an unusable brick? I didn't, but I think I feel the same: my Linux is now an unusable brick.

Yes: I have to reinstall KUbuntu from scratch (or test and install other distributions) to get ride of those errors (or most of them), I will do it (to still see what's happening on KDE 4), but it's not a priority for now. I may be very unlucky with Linux (what a Linux friend told me!) and very lucky with Windows, but I never had to reinstall Windows once in fifteen years (not on the same computer, of course), but I had to install tons of Linux distributions and choose the one "that bugs the less and recognize most of my hardware" and had to reinstall two or three times after bad upgrades (be it the old Mandrake, SuSe or now KUbuntu).

My free time is diminishing a lot.
Lately, I had to abandon BasKet Note Pads development (fortunately, two developers are now continuing it).
I'm going to do paid-job programming all-day long in a few months.
So, when going back home I don't have courage to develop again.
I prefer to play game, watch movies or TV shows... or other non-geeky-things :-)

I weighed arguments for and against KDE and Windows. Having a computer that just works, all the time, and have a computer that feels speedy is now of higher priority than using KDE amazing applications. And in a few months, main KDE applications will run on Windows (I still miss Akregator, the best RSS aggrgator on any platform, Amarok, the world best player, and BasKet Note Pads... no comment: using text files to take notes is somewhat painful ;-) ).
Sure, I will not have Plasma, no Kirocker Music Display to put on the Windows taskbar... but I'll do without them.

All is not lost.
The good news for you is that as I still like KDE, despite not really developing anymore (or not for the moment).
I will be able to continue contributing to KDE by contributing to the KDE on Windows project.

To finish this long post, I would want to thank you all for your support and for having helped me improve both BasKet Note Pads and Kirocker Music Display.