It's not intuitive at all. THAC0 starts at an arbitrary number of 20 and goes down from that, AC starts at 10 and goes down from that. The lower your hitchance or AC the better you're off? It's not logical at all. Particularly when you want all the other numerical values to be highest possible. It's VERY counter-intuitive.
Sure, nerds who have played this system for the last 20 years will know it by heart and won't mind, but for a newcomer it's just mumbo-jumbo, it doesn't make any sense.
Absolutely right and I am one of those nerds. To me it is the same playing one system or another but probably I find the older more charming, getting into negative AC and all. But the consistence of "more is better" offered by 3ed+ system is much easier to understand to new players. AC? AB? Attack roll? More is better. Plus AC0 as a reference was entirely arbitrary, it was an very good armor class but how good exactly? hard to tell for someone new to the system. AC0 is much more logically positioned at "no protection", everybody understands that. There *IS* a reason they kept the same system but turned it around for 3ed and all subsequent eds.