The reason I hear ... over and over again... is that because it is sweet so it makes you crave sweets. I personally think this is ridiculous, going with out sweet things all together makes me crave sweets, having a diet soda helps me not to crave them. I will say drinking a bottle of chemicals probably isn't the best idea for a healthy body, but calorie wise and sugar wise for my diabetes it is far better than drinking the regular ones which are also full of chemicals
Soda in general is bad for you. The sweetener (which tastes absolutely nothing like sugar to me anyway) is not the problem.
There is absolutely nothing beneficial about soda......other than to someone who drinks it likes the taste.
I do not drink soda, except for a small root beer about every six weeks or so. I have never craved it.
Junk food and condiments they make that are low calorie are still not healthy for you. SO...my philosophy is that if you are craving the junk, just have the junk. If you have it in moderation, then it will not be "so" bad. If you prevent yourself a little indulgence, you will only have more than what you originally wanted to begin with.