1. Stable
Any application needs time to be used and tested enough time in order to make it stable. One of the greatest goals of Debian is stability. It's released when it's ready and applications included in the repositories have enough time to be tested through.

I guess most of the readers are already familiar with Ubuntu, but I'm also writing this for new users, which use Linux for the first time. I use Debian for over a year now, but I used both Ubuntu and Kubuntu in the past (especially Dapper Drake and Edgy Eft) and also 8.04 and 8.10 Beta.

I was a Windows user for several years when I decided to switch to Linux, late 2005 or early 2006, I can't recall exactly. I remember that on Windows I was always looking for freeware alternatives to all the paid applications. At the time, I was not aware of the terms 'open-source' or 'free software', and I definitely had no idea about the concepts behind them.