I have not ordered any Butterbeer online, nor have I had the opportunity to try the real thing at Universal Studios.
However, I have made it myself twice, and there is some in my fridge right now!
The first time making it, I used melted butterscotch chips.. and well.. it didn't turn out too well. As a Canadian living in America, it can get frustrating going to the grocery store as Butterscotch is not so easily available in the states as it is in Canada.
I did manage to find some finally, in the ice cream topping section of a random grocery store, and once I made it with the proper Butterscotch, it was great! It was all the buttery and carbonated flavour I was expecting!