I'm not a farmer, but I'll toss in my two cents.
I favor the mandatory labeling even though I don't think there are any health risks associated with them (yet). I suspect that fewer of the most toxic pesticides and herbicides are used on RoundUp Ready crops than are used on other crops.
I think it will make more people aware that they've been eating food with ingredients from GE'ed crops for years (like corn and soy derived ingredients).
I also think it will be interesting and maybe useful to see products developed that can display "NO GMO ingredients". They will command premium prices until competition drives them down ... but then we'll start to see the real financial costs of avoiding GMOs.
Too bad it isn't economically practical to assay and label every box of cereal with the residual amounts of chlorinated aromatic hydrocarbons and organo-phosphates from "traditional" herbicides and insecticides!
As more pests and weeds develop resistances, GE techniques will be used to add more transgenic DNA, and more varieties and greater amounts of insect toxins like bt. I read about one experiment where someone used an experimental 'triple-stacked" bacterial insect toxin.
The GE technology is so powerful that at some point it probably will create things that are detectably harmful to humans or livestock, and I would rather see the precedent established that we DO have to label such things.
Personally, I think the risk of GMOs are in the areas of decreasing crop species' genetic variety, finiancial monopolies, and transgenic gene "leakage" into weeds and other crops.
And I have a question mark in my mind (unsubstantiated by any study I've heard of) that cultivating square miles of crops with gene sequences inserted using Agrobacterium plasmids MIGHT enable some very low rate of conversion into "jumping genes" to accumulate silently until "something" became mobile and spread to other species. Pure SF speculation, but I wonder about thing that only happen once in a billion times. After you have 100 billion blades of modified wheat over the yearss, you would start to observe the rare events.
