So, to actually add something to this discussion, while addition may be easier for more people than subtraction, and higher AC being better may be more intuitive, THAC0 does have one major advantage over BAB: With THAC0, you do the math to figure out what your target number is before you roll, so you immediately know if you hit or miss as soon as the die stops rolling. This as opposed to BAB where you roll first, add your modifiers, and then compare the total to the target number.
Both probably take about the same amount of time and effort, but by front-loading the math, THAC0 makes resolving an attack a miniature dramatic tension arc. You start from the lowest point of tension as you figure out the number you need on the die, then get a little rise of excitement as you roll the die around in your hand, the anticipation as you let it roll onto the table, coming to a climax just before the die stops rolling, and then immediate release as you see the result and know instantly if it is high enough or not. With BAB, that arc gets disrupted by having to add your modifier to the roll result in between the climax and the denouement, which while brief, does make the overall experience less viscerally satisfying. It’s a small thing, but I suspect it’s a big part of why the folks who loved THAC0 miss it, even if not consciously.
What I would like to see is a system that combined the strengths of both approaches. I already tell my players the DC of a check when I call for one to be made, perhaps it would be best to go a step further. Instead of a positive modifier to the roll, give the players a negative modifier to the target number. Sure, then you’re back to subtraction instead of addition, but I suspect it would still be more intuitive than THAC0 due to higher AC still being better, and “subtract your modifier from the target’s AC” being a cleaner way of presenting the same math than “subtract the target’s AC from a number derived from your class and level.”