There are two more short Fallout: New Vegas previews and we're likely to see more of them in the coming days, all based on the same presentation.
There's one from Joystiq:
Speaking of making people happy -- New Vegas sees the return of the karma system from its predecessor, joined by the tracking of your character's reputation among the populace and various factions, including the Brotherhood of Steel, the New California Republic and Caesar's Legion. Depending on your standing with these groups, they'll do everything from ordering hits on you to treating you like royalty when you visit them. Companion characters are also back, though this time you'll have a new "companion wheel" you can use to quickly issue them a wide variety of orders, manage their inventory and more.
In addition to being twice as large as Fallout 3's, the arsenal in New Vegas consists of fully customizable weapons, with various mods to be bought and found on your adventures. These will include everything from special ammunition to larger-capacity clips, scopes and more. If new weapons such as a grenade machine gun and a golf club are anything to go by, there'll be a lot of new, outlandish and highly desirable armaments to acquire. Also, in an effort to make the game more FPS-player-friendly, you'll now be able to do a proper zoom aim down the sights of all weapons. The non-V.A.T.S. combat presentation has been enhanced with dramatic slow-mo as well, which can be turned off should it get to be too much.”
The VATS combat system has also been tweaked, allowing for melee attack commands. Just don't expect a massive difference in the way the successful targeting system worked in Fallout 3. But do expect a greater variety of weapons, thanks to new weapon mods that let players customize their firearms with larger clips, scopes and specialized ammo. More outlandish weapons like the grenade machine gun and golf club will also add a little variety to your post-nuclear excursions.”