I can only speak from personal experience, but *I* do get insulin spikes from aspartame. I'm hypoglycemic, so I can really tell when I'm getting an insulin flood. It doesn't happen EVERY time, but often enough so that I avoid it. I've spoken with other low-carb dieters that can't tolerate the stuff, or that it stalls their weight loss.
Aspartame is also said to convert to some really nasty chemicals when heated to body temp. It is rumored to cause brain damage. Also, doesn't keep it's sweet taste when you cook it.
I use saccharin - recently proven to NOT cause cancer as previously assumed for cold drinks/food and coffee, as it is EXTREMELY cheap.
I use splenda for cooking/baking or for when sugar-taste is REALLY important (like on grapefruit) and the saccharin bitterness would be too much.
Splenda is cheapest and lowest carb in the bulk box. I get the box for less than $3.50, usually.
Fawn