I've tended to avoid the GM debate here because ultimately I'm not that concerned about the technology. I'm concerned about its uses (which seem to be primarily about supporting - indeed, forcing - the use of stupid and unsustainable farming practice in the name of higher corporate profits), I'm concerned about consumer rights and product labelling, and I'm concerned about government secrecy and corporate lies. I am not concerned about "spiritual pollution", "playing god", or "interfering in the natural order".
I am however concerned about this: a study suggesting the use of GE crops (and particularly Bt corn) is a possible cause of a massive decline in bee numbers in North America. We depend on bees - they pollinate plants, and by doing so support a third of our food chain. If this decline continues, then we could see crop failures and significant hardship as a result. If our current GE plants are causing it, then it would seem to be a strong argument for ditching them and using much better testing in future.
(Hat tip: Qarl)