But Mongo DB being buggy isn't a reason to need to use an SQL database vs. a NoSQL store. An SQL database could be buggy as well (I still use Postgres and comparing anything to that quality-wise is just going to bring sorrow for the thing you compare it to ;) ).
FWIW, it's been spotless for us so far. Our needs aren't web scale, but they're big enough to need scaling features.
The main issue with MongoDB is that it's so easy to use and seems like it scales, but soon you're invested in it to the point of refactoring being a serious engineering effort, and you're stuck with something that doesn't actually offer real scaling features.
So, it's less "nosql vs. sql" and more just "don't use mongodb".
FWIW, it's been spotless for us so far. Our needs aren't web scale, but they're big enough to need scaling features.