Well the fact that so many people answered with really stupid responses tells me why FNV doesn't work. People keep buying the crap regardless of whether or not it works. Rampant fanboyism ftl.
I spy with my little eye... a troll.
I have had comparatively few issues with my game on an Xbox 360. The occasional freeze at a load screen. A couple of freezes on my first couple of approaches to Novac (and I mean my 'first' - before patches, just after launch). Occasional clipping issues. That's about it. I haven't had a single quest fail that didn't have something to do with my actions.
Obviously you either want to be talked into it, or you want to stir up controversy and create drama about it.
If you want to be talked into it, I say: "Get the DLC." Of course, I have absolutely no idea what kind of gaming you enjoy, so I could be completely wrong. But I still say: "Get it!"
If you're going the other way... well, congratulations! Mission accomplished.