It's still Scotland's leading soft drink and you can buy the original high-sugar recipie:
Any changes made before I started drinking it are merely historical baggage, but any changes made after I started drinking it have a fundamental effect on whether I consider it the same product. See also: "New Coke".
(Also, I can taste Aspartame -- so while many people might say that the low sugar variant is sufficiently similar in taste, I really don't enjoy it. Although, as I posted above, this is probably a good thing.)