I was curious, so I tried this recently:
Brand: O-So Butterscotch Root Beer.
Origin: Mukilteo, WA.
Purchase Place: Frattallone's Ace Hardware, St. Paul, MN.
Sweetener: Cane Sugar.
Review: This was HEAVY on the butterscotch. It had the smoothness and creaminess of a root beer, but the flavor was about 90% butterscotch. Ideally (for me), a butterscotch root beer would taste about 20% butterscotch and 80% root beer. If you REALLY like butterscotch, then try this because you'll love it. If you just think butterscotch is OK (like me), then this could be too much for you.
Score: 3.5 out of 10.