I've heard this a lot. In fact, it's usually the first argument against New Vegas people say. Which is fine, but I'm wondering how valid of a claim it is. It is true New Vegas does "push" you into making a huge horseshoe from Primm to the Mojave Outpost to Nipton then up to Novac. Admittedly, this gets boring after the third or fourth playthrough. However, while it would seem that the paths north to NV are blocked by high-level enemies... I really don't think this is the case. Just north of Goodsprings Cemetery, there's a path blocked only by a handful of Cazadors. You can outrun these with a bit of effort. And the first thing you see? Red Rock Canyon. Which makes me think this was intentional, as you can get a lot of dialogue from Goodsprings residents about the Great Khans. Obviously the game wants first or second time players to go to Nipton and be exposed to the Wasteland (and see the NCR and Legion), but I feel that this path was equally intentional. New Vegas is very forced otherwise, however, but I think that it isn't "railroaded" per se.