I guess I could be labelled as a Diet Coke fanboy. Particularly since there's several people around here who'll claim they don't know me if someone mentions my name, but as soon as someone mentions 'Diet Coke Boy', they're suddenly like "ohhhh, him".
There is a difference in taste between regular and Diet... don't even get me started on that. There's even a difference in taste between the Diet Coke we get here in the UK and the stuff we get imported from continental Europe. A lot of takeaway places will get cheap imported stuff from Germany, France, Poland and even as far afield as Georgia and the Middle East, and it tastes completely different.