Over the last couple of years, Debian Linux has released new stable versions about every two years. This pace is great for progress, but there is a serious problem. This problem is related to their support for older Debian stable versions.
If you read the quote below from the Debian Security FAQ it will dawn upon you:
Q: How long will security updates be provided? A: The security team tries to support a stable distribution for about one year after the next stable distribution has been released, except when another stable distribution is released within this year. It is not possible to support three distributions; supporting two simultaneously is already difficult enough.
Translation: after 3 years, you must apt-get dist-upgrade or be screwed, you will no longer receive security updates!.
Apt-get dist-upgrade or die, so to speak.
The problem is that the whole apt-get dist-upgrade thing is cool and all, but in my experience, it doesn't work. Even a simple web server gets screwed up badly. You need to diff all config files and spend quite some time reviewing all changes and fixing the broken stuff.
I'd rather spend the time creating a new fresh Debian installation based on the new stable release than on tinkering with the aftermath of an apt-get dist-upgrade. But that also takes a lot of effort.
I want an operating system that will be supported for the next five years so I don't have to spend time on this upgrade process every 3 years for a system that is otherwise fully functional and rock solid.
To tease you a little bit: Microsoft Windows operating systems are supported for ages. But that's not an option for me, I stick with Linux, but Debian does not provide this kind of extended support.
Ubuntu releases LTS versions: Long Term Support versions that will receive security updates for at least 5 years.
All the goodness of Debian but with longer support. That is the reason my shop will switch to Ubuntu Server LTS.