I'll pick it up too.
I liked San Andreas a lot, but the guys from Rockstar just keep making the same mistakes over and over again. They always make the games bigger with more stuff to do, but most of it is completely useless imo.
My advice: Keep it relatively small, polish the graphics, include every part of the map in the main story and focus more on the driving aspect( that's what i loved in the original DRIVER game btw).
It would also help if they released beta versions of the game earlier for the magazines, because feedback can help.
But as of now, GTA is a game which doesn't live up to its potential.