Those are relatively low system reqs compared to current games. They're basically the same reqs as Fallout 3, so I'm guessing they didn't change much in the engine.
Basically, FO3 required a Single-Core 2.4 Ghz processor, 1 GB RAM, and GF 6800+ card or ATI X850+.
Doesn't seem like much has changed w/ New Vegas - just the double-core 2.0 Ghz requirement.
I'm looking forward to New Vegas but from what I've seen I get the feeling it's gonna be more like an expansion or "Fallout 3.5" since it takes a lot from the original.
A lot of New Vegas to me doesn't seem really much new - agreed. The scenery, back-drop, and game-world looks like the biggest changes here. There's a few nice new things and tweaks - such as you can aim down the sights and certain melee weapons actually have special attacks of their own in VATS - but yeah, is there really anything else new here?
Hopefully, Obsidian add the kitchen sinks, in terms of having LOTS of content - especially on the side quests and all. I'm betting FO: New Vegas will take longer than most new games that are full-price - since it's still a RPG and all.