Rolling release is by definition "unstable" in the sense of "tending strongly to change, not constant, fluctuating." (definition from thefreedictionary.com/unstable)
That being said, Arch is a popular and high-quality distribution. Many users successfully run it with minimal breakage with the help of the update warnings on archlinux.org (always check there before updating), the excellent wiki, and the Arch forums. I personally prefer a stable distribution (Debian, CentOS, Slackware, Ubuntu, etc.) but my experiments with Arch have been overwhelmingly positive, I would recommend it without hesitation for someone seeking a rolling release for whatever reason.