Splenda works best as a sweetening "enhancer". With a little sugar it's fine, but by itself as the sole sweetening agent, it's pretty gross -- to me at least.
Why is everybody so paranoid of a tablespoon of sugar? Do you really think that's going to make the difference between looking like the current you and looking like Ronnie Coleman?
Maltodextrin is the worst, not becaue of its glycemic index but because it isn't very sweet. You need 4 tsps ( about 16 carb grams) to equal the sweetness of one tsp of sucrose -- 4 carb grams -- not bad, and it makes all the difference.
Stevia has a bit of a "maplely" aftertaste and has shown to have anti-androgenic properties. (As does licorice)