I've been looking into Splenda, or rather Sucralose. It's very intresting, it is simply a chlorinated (a few OH groups are replaced with Chlorine) sucrose (common table sugar) molecule.
It is somthing like 400 times sweeter than sucrose, which means you need less of it to sweeten food/drink. It's behavour is very similar to surcose, and does appear to be less digestable than sucrose.
It was dicovered around 20 years ago, but only last year was it approved for human consumption in Europe. (Canada since '92 and the US since '99 IIRC).
It look like a winner, my only criticism is that it has a strange (slightly bitter) after taste.