We all know that sugar intake should be limited in general, but people seem to look on high fructose corn syrup especially poorly. Why is it any worse than sucrose? Crystalline fructose? Other sweeteners such as stevia or aspartame?
I think research is inconclusive on this matter, I don't believe there has been consistent scientific proof that HFCS is as bad as it was blamed to be recently.
Aspartame is also similar. While generally seen as "bad", research seems to suggest otherwise. I personally avoid it, just to be safe.
On a personal level, I think that as long as you have a fairly healthy diet (without too much "processed" food in it), you should be perfectly safe from these sweeteners whether or not they're "the devil". If you are, on the other hand, eating a lot of processed stuff, sweeteners are probably not the main issue with that type of diet.
HFCS is usually 55% fructose and 42% glucose, while sucrose is 50% glucose and 50% fructose molecule - this is why HFCS is slightly sweeter.
Glucose can be used as energy in every cell in the body, while fructose, like ethanol, must be metabolized in the liver. Fructose in nature is fairly rare (small quantities in fruits, packaged in lots of fiber) so it is not surprising that the liver is not prepared to process the large quantities of fructose in our current western diet.
While HFCS is not in itself worse than sugar, its low cost (made from subsidized corn instead of highly taxed sugar canes) makes it very attractive for food manufacturers to put HFCS into everything - soda, milk, sauces, bread, you name it.
So, instead of ingesting a few grams of fructose, many people on a western diet now ingest several ounces, and that, depending on who you ask, is bad, very bad, or the single leading cause of the obesity epidemic.
Other sweeteners are not sugars; if they're harmful, they're harmful in completely different, incomparable ways.
For more information about the metabolism of sugar, see: Sugar: The Bitter Truth
Fructose (the substance enzymatically produced from sucrose in the production of high fructose corn syrup) is found naturally in fruits, vegetables, and grains. As with any sweetener, eating too much of it will naturally raise the amount of carbohydrates in your diet and upset the natural way in which the body expects to be nourished.
The only difference in the two is that fructose is absorbed into the body slightly faster than sucrose, meaning that eating excessive amounts of fructose will yield slightly more weight gain than sucrose over a shorter period of time, but will have little to no relative effect over the long term: if you overeat, whether it's sucrose, fructose, or fat, you'll gain weight. Period.
Much of the processed and "fast" foods now contain added sugar or high fructose corn syrup for seasoning purposes, and those foods which have been artificially sweetened should be avoided generally. It is always healthier to eat natural foods in their raw form.
Calorie free sweeteners and sugar alcohols are a matter of debate, and from studies conducted seem to largely depend on how an individual responds to them.
High fructose corn syrup has gone through processing to turn some of the glucose into fructose which makes it about 3x sweeter. The big difference is how the body metabolizes and stores the two. Fructose goes right to the belly which gives you a better chance of heart attack and stroke.
Some studies have even found trace amounts of mercury in high fructose corn syrup.