Its also absolutely huge, and not just in terms of raw acreage. This version of Liberty City is filled with vertical spaces and seamless building interiors to explore, and a lot of the cool stuff is hidden up on rooftops - if you can find a way to get up there. You will be able to climb ledges, ladders and fire escapes, so it's all a matter of knowing where to look.
Driving feels a lot different this time around; in many ways it's smoother, but more realistic handling (especially on the crappier, clunkier cars) also means it's a lot harder to brake or turn corners at high speeds.
Overall, this is a must buy game, and the best yet.