Popped the game in yesterday and played through the first mission. Looks and plays exactly like Vegas 1. I'm wondering if there was any technical improvements done here, because I dont really see it (yet).
There seems to be an new, interesting system they've implimented into the game. It's almost like a kudos system where you get rewarded XP for different things. I can only speak on what I've exprienced so far, not the entire system. But, early on I took out a guy from behind with a head shot and saw a little "+3" pop up in the corner. Upon further inspection I saw, in the options menu, there was a submenu called A.C.E.S. and apparently it's a little system that rewards you with XP depending on your play style leading to new weapon and equipment.
Also, I should note that when I put the game in it realized that I had played (and beaten) the first game and welcomed me back, unlocked a few things (equipment) and added +1,450 XP. Interesting...