I loved NV overall. But if I had a largest complaint it was without question...
It just wasn't populated as densely as FO 3. There was always something over the next hill in FO 3. 4 is pretty similar. But NV, you could walk for several minutes in one direction or another and encounter NOTHING. I guess there's a kind of sense that makes in creating an atmosphere... but it was supposed to be an entertaining game. Atmosphere is important, but having something to do other than press forward to walk is kind of important as well. I've played FO 3, 4, Skyrim... a lot of games with a self-imposed restriction on fast travel. And its easy. I'd probably rather shoot myself than try that in NV.
Honestly the emptiness wasn't a problem for me, as there are stretches in FO 3 where you can find yourself in the middle of nothing. Actually one of my favorite moments in FO 3 was exactly that. I had been sneaking around with Dogmeat at night, listening to the radio, and got tired of the loop of oldies, so I turned it off. I was just kind of creeping along, and the ambient music kicked in. It was a clear sky, so lots of stars were out, there was the subtle wind blowing effect going on, that spacey music was playing, and Dogmeat was calmly panting next to me. And with my headphones on, and playing at night, it was one of those moments where you find yourself, at least senses-wise, feeling IN the game. I stopped for a second, just kind of looked around at the beautiful stillness, looked down at my loyal pooch, and realized I'd had a Gaming Moment. And it was specifically because nothing was around.
So the fact that a desert, is, you know, desert like, is fine. I just mean aesthetically, I found the map so samey as to be boring.