I would disagree. For a production machine definitely but maybe not a desktop machine. I have run unstable without any problems for 18 months. Maybe I've been lucky but debian in all its forms is one of the most stable linux distribution I have run."Sid" is the testing kernel and is more advanced than "Sarge" and will cause you problems; stay away from that one.
This has already been discussed in the list, so I will not repeat what has already been stated -- sid/unstable is *not* about the stability of the system/packages, but about the fact that it is being constantly upgraded. Depending on what you wish to run on your machines, that can be a problem. Consider, for instance, closed-source software which has strict dependencies on library/kernel versions or such, and you may understand why some people would trade upgrades for "stability". However, my experience with Debian as a desktop system, using almost 100% Debian-packaged applications, couldn't be better. Most problems I have had come from binary-only kernel modules (which Debian discourage anyway), but having both an ATI video card and a ndiswrapper-only WLAN adaptor, I cannot blame the distribution.