I've enjoyed the game immensely so far. I'd say there's a lot more difference than just 'it's in a desert.'
Could you explain how? Aside from the obvious "upgrades" that come from the fact that it's newer (such as companion menus and such), it's just fallout 3 in another setting with fewer perks and skills.
One thing I do really like, though, is the hardcore or whatever it's called mode.