So far, practically all the "research" I've seen that makes Splenda out to be bad is by people who make a living offering alternatives.

There was one peer-reviewed study someone showed me that seemed totally legit and unbiased, which showed that rats fed Splenda had a slightly higher occurrence in cancer. I don't know if it has been replicated yet.

My opinion is that Splenda, Aspartame, whatever you want to call it is safe and the sugar or caffeine in the food you eat is much more likely to affect your health.