Besides Ubuntu as an OS on my machine, I'm also using Debian GNU/Linux 7 Wheezy for months now. I'm enjoying using this latest stable version of Debian because it really is a stable version. I never encounter a single error while using it. That's the main reason why I choose to use it for some stuff I'm doing. If you are looking for a stable OS and have never use Debian before, I highly recommend to install and use it.
In Debian stable, I can get many software and applications which are complete enough (at least for me) for everyday regular tasks. Although for some applications I used to use in Ubuntu I have to find alternatives, but they are there. Software versions in Debian stable are a bit outdated compared to those in some other Linux distributions but that's not really a problem because most of the time I don't really need new features that comes with the newer version of most applications.
But today I was thinking of adding some more software and also to get some more up-to-date version of apps. I was adding software sources from Debian Testing (currently Jessie repo) by using the powerful Synaptic Package Manager app. Then I open the software sources utility to add lines to software sources list. While I was clicking tabs in Software sources window, I noticed something strange, but funny :)