Source 1
Source 2
So far we're getting a new chopper and some new weapons... but hopefully this time there will be some cooler new vehicles.
The new bikes were good last time, but the gun van and tow truck were lame.
Sky diving looks like it could be real fun though... imagine the shoot outs we'll be having in multiplayer now.
UPDATE #1
New details from XBox World (UK) preview.
The preview also featured four new screenshots, one of which proves the Maisonette 9 nightclub to be a near-exact replica of NYC nightclub Bungalow 8.
Source
Meet Tony Prince Video
https://www.youtube.com/watch?v=DGcI4BACd3I
Weazel News Special Report: Guns In Liberty City
New minigames confirmed:
2 basejumping games, 1 checkpoint type and one where you have to land on the back of a moving truck.
Nightclub mingame, where you have to manage nightclubs including getting the party started by dancing...