Aspartame, sucralose, even stevia--it's likely that none of them are particularly good for you in large quantities, just like anything else. Then again, neither is sugar or high fructose corn syrup. Empty calories. Eat real food, drink real juice, wine etc. in moderation.
In my opinion, Monsanto is a shitty company, but not for aspartame--for the terminator seeds they produce and dominate the market with. That, in my opinion, is the true danger of Monsanto. If something should happen, and the majority of farms have terminator seed crops, there is no way of easily sustaining the food supply. For that reason alone, I will not buy anything put out by Monsanto.
I like to garden and tinker around with plants a bit, ala Gregor Mendel. If those are the only seeds available, I can't do it. I don't want a garden that is genetically engineered to survive RoundUp (tm). Nasty chemicals in that shit that will end up on food you eat and in the water supply.
There are better ways.