Among other things, the Mercola article reveals that:
As of 2006, only six human trials have been published on Splenda (sucralose). Of these six trials, only two of the trials were completed and published before the FDA approved sucralose for human consumption. The two published trials had a grand total of 36 total human subjects.
36 people sure doesn't sound like many, but wait, it gets worse, only 23 total were actually given sucralose for testing and here is the real killer:
The longest trial at this time had lasted only four days and looked at sucralose in relation to tooth decay, not human tolerance.
If you remain unconvinced after reading Mercola, I suggest a Google search for "Dangers of Splenda" and taking a look at some of the sites that come up as a result.
Stevia would be a good natural alternative. A better tasting, harder to find and more expensive alternative is Lo Han (also called Luo Han or Lo Huan). You can find it on the net, and, although it is pricey, you only use a tiny amount - since Lo Han is 200-250 time sweeter than sugar, which it tastes almost identical to.