Stable doesn't necessarily means there aren't any bugs, it just means it doesn't change or changes are minor. Of course most bugs shouldn't be a show stopper, though annoying they should have a way to bypass them or simply not have that great a impact.

I recall when using and regularly updating Arch, a library update borked a software dependent on it — a software required for a Uni class mind you — and while I managed to get it working afterwards, I had to stay awake through the night. That's the difference between stable and rolling release, that wouldn't happen as easily on Debian stable.

For most users a rolling release model is fine, for servers, it's not.