Can someone explain to me ...

the only thing i know about is it has more aspartame than regular soda & there is controversy regarding the safety of aspartame

There is a whole long thread where all sorts of interesting arguments have been made on both sides. Hold on I'll find the link......

Here you go, 12 pages of excitement, rather than everyone rehashing the exact same arguments again:
http://www.myfitnesspal.com/topics/show/412923-diet-soda-or-no-diet-soda?hl=diet+soda

There is a whole long thread where all sorts of interesting arguments have been made on both sides. Hold on I'll find the link......

Here you go, 12 pages of excitement, rather than everyone rehashing the exact same arguments again:
http://www.myfitnesspal.com/topics/show/412923-diet-soda-or-no-diet-soda?hl=diet+soda

good idea, thanks. I certainly didn't want to start a debate

Get ready for some exciting reading. ;-)