Every artificial sweetener I've tried gives me a rather nasty aftertaste. Very bitter, and it sticks around for a while. No other ill effects. Splenda and sorbitol are less awful than most, but they all taste bad enough that I won't have 'em willingly.

Yay for weird taste genetics.

I find a small amount of lemon or lime juice in plain water tastes sweet to me, particularly when dehydrated. So if I must have something and I'm avoiding sugar, I do that.