I wonder how much money the load time slowdown has cost Rockstar -- given their revenue from "Shark Cards", which are bought by players who want the fun of playing with all the expensive in-game items without spending time grinding for them.
What's the correlation between being averse to spending time on less-fun aspects of the game (to the point that you'd pay Rockstar extra money to get only the more-fun time)... and being averse to waiting for long load times, when you just want to play a quick session of more-fun?
Given Rockstar's investment in a steady stream of new big-ticket in-game items, and their huge revenue from that, I wouldn't be surprised if the slow load times cost them many millions.