Here's another researchers opinion:

http://www.reuters.com/assets/print?aid=USTRE63C2AJ20100413

excerpt:

But recent findings by Kremer and other agricultural scientists are raising fresh concerns about Monsanto's products and the Washington agencies that oversee them. The same seeds and chemicals spread across millions of acres of U.S. farmland could be creating unforeseen problems in the plants and soil, this body of research shows.

Kremer, who works for the U.S. Department of Agriculture's Agricultural Research Service (ARS), is among a group of scientists who are turning up potential problems with glyphosate, the key ingredient in Monsanto's Roundup and the most widely used weed-killer in the world.

"This could be something quite big. We might be setting up a huge problem," said Kremer, who expressed alarm that regulators were not paying enough attention to the potential risks from biotechnology on the farm, including his own research.