It has a glycemic index of 56-62 depending on the fructose to glucose ratios. That's considered a moderate GI, not extremely high. Sucrose (standard table sugar) has a GI of about 65. White bread (70+) and baked potatoes (about 86) have a higher glycemic index.

I don't disagree that we would be more healthy and less fat were corn not subsidized. But that would be because sweetened foods wouldn't be as cheap so we couldn't afford to eat as much and the markets for them and drive to sell them to us wouldn't be as huge. Not because HFCS is, in itself, less healthy than any other sugar source.