There are concerns about GM crops for a reason. To stimulate the expression of the added genetic material, you use promoter genes. And the big question is what these promoter genes will do to the crop or to the person or animal (GM soybeans) eating it. So some reservation is appropriate.
It's unfortunate that an extremely evil company (Monsanto) has made it nearly impossible to get some decent research and discussion possible about what we're doing here. Also the whole agricultural-political complex in general doesn't have a good reputation for a reason.
In the case of Roundup ready crops the solution is, IMHO, not dousing your crops with a herbicide, but to use other techniques (less monoculture!) or improved crops. We see the problems pop up already in the US, where resistance to Roundup has become a serious problem.
It's a bit reminiscent of the use of anti-biotics; overusing them creates selective pressure for the bacteria, which stimulates the development of resistance. So long-term this is not the way to go.
And as to the saving millions of people part; as far as I'm concerned the bigger problem to tackle is population growth, but that's a completely different discussion.