The visual effect of ADS is fucking terrible. Just as bad as the function of it in most games.
But there's also Sprint, a far bigger issue. I did say over at HaloGAF thread that if i had to choose, i'd rather get rid of Sprint as the "smart scope" can be tuned to be nothing more than visual overhaul of the scope (unlike now, as it gives accuracy boost to some weapons apparently).
Sprint so terrible. And i don't think the shield-regen "compromise" solves the problem. Sprint is still needed for abilities (ie it is not an optional feature), it still makes the maps larger, it still allows easy running away. And it affects the control scheme negatively too. Can't play with proper Bumber Jumper (grenade switch on A, X for special ability).