Since 1985 in the U.S., Coke has been made with high fructose corn syrup instead of sucrose to reduce costs. [...]
Though the Coca-Cola company claims that there is no difference in taste, many people claim to prefer Coke made with sugar. [...] Kosher for Passover Coke is also made with sugar, rather than corn syrup, due to the special dietary restrictions for observant Jews (Orthodox Jews are prohibited from consuming corn during this period) during the holiday.
HFCS, like most corn products, is very cheap in the U.S. because of corn-farming subsidies and very high supply. Most packaged foods and drinks in the U.S. use HFCS instead of sucrose (regular "sugar") only because it's significantly cheaper, despite some preliminary research that may indicate that it's unhealthy and leads to obesity and diabetes. (I think this is ignoring the obvious: overconsumption of any sugar leads to obesity and diabetes.)
Many die-hard Coke fans are convinced that its reformulation with HFCS damaged the taste, claiming that the sucrose version was less "sticky" or had a better aftertaste. To test this assertion, I purchased Passover Coke and did a blind test (good idea, Tiff, and thanks for conducting it) to determine which tasted better.
That's about it. If I was a die-hard Coke fanatic (I'm not, and I rarely drink soda), it would certainly be worth trying to find some Passover Coke for curiosity's sake. But it's not worth driving to a different state or mail-ordering it.