Short bio: Computer Scientist, FOSS supporter (read more)
Tux Machines (TM)-specific
Every two years or so, Debian puts out a new "stable" release. This is my favorite distribution because of the minimal number of bugs and the huge software repositories and the powerful package manager. Right now, Lenny (5.0) is the stable release, and Squeeze (6.0) is in testing. Sometime "soon" Squeeze will get frozen, which means the regular flow of package migration will stop, and from then on it will only get bug and security fixes through a method of back-porting. Once the number of "release critical" bugs is reduced to an acceptable level (which used to mean 0, more recently it means 50 or so), then Squeeze will be released as the new stable version.
As a desktop user, I find that Debian is usually ready enough for me sometime before it's released. This time around, I've been running a Squeeze demo on my laptop (a Thinkpad T41) every few months, and as of May it's been my main install. In fact, to me it's better than Lenny now. (Perhaps this is why Ubuntu just released a new LTS version? They depend on having a stable-ish Debian moment in order to do LTS, it seems.)