GM crops are 100% safe to eat. Up to date, the natural pesticides produced by such plants are all stuff that is harmless to people, so unless they start inserting genes for botulin or whatnot, such plants and animals completely safe for consumption. Another common misconception is that meat engineered to produce extra hormones can somehow affect human development. This is rubbish, as hormones are delicate molecules that do not survive the digestive process (never mind the trace quantities they will be in, and the species differences). In fact, GM crops and livestock are often more nutritious because of their engineering.
What is of concern is how GMOs interact with our environment, a point Mike brought up earlier. A prime example are genetically modified salmon on open-water fish farms. This is downright irresponsible, as the GM fish can and do escape, and impact the natural salmon populations. The same can be said for pollen from GM plants- they might theoretically interbreed with native species or otherwise become invasive, or otherwise impact the local environment.
The final point is completely unrelated to biology, and that is the patent system. I do not claim to have any expert knowledge in this area, but it doesn’t take a genius to see there are bad things happening that are probably detrimental to our farmers.