Things move from sid to sarge (unstable to testing) When they've been running without incident or major bugs in unstable for a while.
Basically Unstable is the cutting edge of everthing, (or the bleeding edge if you prefer
). Testing means yep it does work and doesn't crash mostly.
Stable Well is absolutley Stable and won't be upgraded ever. (Just occasional security fixes.)
When Sarge has a complete set of everthing and is a complete system for all ports in becomes the new Stable, and replaces Woody. A new Testing is created, with a new name.
SID is always Unstable.
They reckon Sarge is going stable in December. (Well They reckon anyway).
As for volitile, Not really Never had any major crashes, (touch wood).
Where usually just a point or two behind CVS versions, be we do have a few of thoose as well.
Anything that doesn't work one day, gets fixed the next usually. and Debian SID is usually ahead of every other distro for new stuff.
makes me laugh when people say Debian has old stuff.
