I should mention that I don't work in IT and I'm not an expert, but I have been running debian for a few years now, and Linux for a little longer than that. i.e. all my boxes are for personal use.
I have always run sid. Before sarge went stable, unstable was pretty good. I had a few hiccups but never had one showstopper between a laptop a desktop and a home server dishing out music and movies. After sarge went stable, well, it's been a learning experience. Once, yaird was updated the same day the kernel was, leaving two machines unbootable. I had to revert to earlier kernel version. I've had issues with Xorg locking up. At another point I couldn't enable dma. All issues required some time googling and got solved.
This is fine for a home setup. If my comp is unusable or sluggish for a day or so until I can pay attention to the problem, it's not the end of the world, I just can't email lovenotes to my gf. In a production environment where my job depended on stability, I wouldn't touch sid.