I have one that was installed by the dealers contractor. It works ok, but is definitely not as nice as the CC on my Saturn. I have a manual transmission Spectra5. The CC is set to shut off only when I touch the clutch and not the brake, supposedly the only way they could set it up, which seems unsafe to me as every CC car I have driven shuts it off when you hit either the brake or clutch. Anyhow, I have adapted now.
It is nice on the long steady highway, but not sure if it was worth what I paid. They should make CC standard.