Have you used Debian unstable/testing on a production/personal server?

I prefer Debian GNU/Linux as operating system for servers. I generally tend to think stable is the best choice. But I use unstable/testing on the desktop.

Are there real cases of servers using Debian unstable/testing?

Two years ago we needed PHP5 in production environment. Debian stable wasn't yet there and for some reason, backports was not considered. We let our hosting company install testing and it worked nicely.

However now that we need to update to Lenny, we just can't upgrade the production system on the go, we've to clone the system, upgrade, test, etc. because the version numbers of many applications has greatly increased over the last two years.

So this now creates work for us (internal work hours) and also payload for our hosting comapny which we've to pay.

Lesson learned; or at least, next time I'm prepared to what comes in the future.

If it's production, then don't use unstable. Use stable and backports instead, and testing if you must. Testing is ok for a desktop machine you can afford to break for a day. It's not for production.

Also, Zoredache mentioned apt-pinning. It's a little confusing at first, but worth learning. If you go that route, start with reading the apt_preferences man page. The key to apt-pinning is keep it simple and start small.

One last thing about the relative stability of the releases. Stable is always rock-solid, and testing is usually as reliable. When there's an impending release, testing gets much more stable and unstable gets a little stagnant. After a release, testing becomes a little less stable and unstable becomes buggy again.