Does not have depth of GTA3
Graphical glitches - namely aliasing, poor FPS when things get busy, and vehicles appear sideways off in the distance for a split second then disapear.
Functional glitches - jump on a car and hit Y and you are instantly inside, and intermittently, when you dive out of a moving car, you transport instantly to a rail station and the current mission is scrapped.
Sound glitches - stand on any street with no cars on it and you still hear the sound of cars driving by.