One of the greatest criticisms of Debian is that its release cycles are too long. Debian stable release is seen as often as Ubuntu’s LTS release. As a server solution this doesn’t present a problem at all, it can even seen as a pro. However, for desktop use and for your average Joe who needs to have the latest software and is unable to get it, this may well present a problem. Of course he can always turn to backports to get what he needs but by the time you have finished reading this very sentence, Joe has already moved to Ubuntu.
Okay, so what is Debian CUT?
The idea stretches back more then 2 years, to Joey Hess proposing the idea of “Constantly Usable Testing“. For users/developers who can’t wait ~2 years to see new Debian release, they usually turn to Debian “testing” branch. To clarify, “testing” images are released weekly, but most of us in Debian don’t recommend you jump to “testing” by installing it from weekly image, but rather by upgrading from stable. To make the situation even worse, these builds frequently don’t work due to all the changes that have been pushed from unstable.
But this is where Constantly Usable Testing idea comes in.
rest here