I'm not that keen on Splenda, although I've not had any bad reactions from it. Just find it has a slight unpleasant after taste. But I drink pepsi max and coke zero all the time, and don't really notice any aftertaste.
I've been using xylitol for adding to yoghurts and fromage frais which although it's a bit granular, is actually v pleasant. Quite expensive though, compared to splenda.
I've also tried Stevia, both liquid and powder, and it's really v strong - almost too strong! I think you
need very tiny quantities of Stevia otherwise you get a liquorice aftertaste. Everyone to their own taste, I guess.