I think it's a bit disingenuous to paint with such a broad brush the level of knowledge there is about the long-term effects of GMO foods. Numerous studies have been released[0] and more published every year seem to lean towards minimal to no perceivable negative effects.

EDIT: I will grant that all of these studies deal with animals rather than directly at effects on humans, but it doesn't seem there is compelling evidence thus far for one to assume there would be a significant difference.

[0] http://www.fass.org/page.asp?pageID=52&autotry=true&ULnotkn=...