I've been a fan of GTA since I played the first game when I was 12, and GTA3 was a revolution in the way that I thought about games, so this will be a day 1 purchase for me.
I love all the games in the series, but I wasn't a fan of the crazier elements they introduced in San Andreas (jet-packs, stealing military jets for a super-secret government agency), and while I was glad that they took a more serious tone in GTA4, there's no denying that it was missing some gameplay elements and the later missions got kinda repetitive. So if they keep the serious tone while adding in some of the missing features, such as car customisation and a wider variety of weapons, I'll be very happy.
I still haven't finished "The Ballad of Gay Tony." I can't get past the section where you have to steal the helicopter and destroy the yacht. My flying sucks too much to be able to take down the yacht.
I remember trying to 100% that mission, which meant I had to chase and destroy the three boats without taking any damage. That was a pain.