Has anyone at Obsidian stated how large the open world will be, relative to the previous game? 
 
It needs to be at least as large as 3's or im wicked disappointed..

I'm not sure if Obsidian has said just yet. I'm hoping it's huge though.

iirc, they said it would encompass the dam, a large majority of the city, and some outlying areas around the city. IF put to scale they are talking about the strip and the old strip (Freemont Street) in the city which is a rather large area. 
 
IGN wrote 

 Fallout: New Vegas is promised to be as large as Fallout 3, both in terms of the number of gameplay hours it offers and the size of the world to explore.    Once you reach downtown New Vegas there are a host of casinos where players can try their hand at slots, blackjack, and roulette. So far Bethesda has revealed six casinos including Lucky 38, The Strip, Gomorrah, Vault 21, The Ultra-Luxe, and The Tops.    

" iirc, they said it would encompass the dam, a large majority of the city, and some outlying areas around the city. IF put to scale they are talking about the strip and the old strip (Freemont Street) in the city which is a rather large area. 
 
IGN wrote 

 Fallout: New Vegas is promised to be as large as Fallout 3, both in terms of the number of gameplay hours it offers and the size of the world to explore.    Once you reach downtown New Vegas there are a host of casinos where players can try their hand at slots, blackjack, and roulette. So far Bethesda has revealed six casinos including Lucky 38, The Strip, Gomorrah, Vault 21, The Ultra-Luxe, and The Tops.    

"

I thought New Vegas was slightly smaller then Fallout 3.

from what ive heard it is the same size as 3 give or take. but there is much more to do

It'd be cool if a large part of the playable area took place within the Vegas city limits...sort of like a big chunk in Fallout 3 was inside DC. But ya know, Vegas isn't totally dinked.

its probably just gonna be about the same size as fallout 3s standard map is.

i would be very pleased if it was the same size as three, i though that the map was perfect, not so huge that you can't remember your way around but big enough that exploration is possible.

Bigger than Kanye Wests ego!!!