There is a lot of genuinely good content on Quora. They went out of their way early to attract some high-level Silicon Valley talent, and that brought in a fair number of good writers. It was really cool, for example, to have physics professors explaining the Higgs Boson at the time of the CERN announcement.

It degrades over time, partly from simple reversion to the mean, partly because a number of topics have simply been talked to death. That's why they started paying people to ask questions. There's still good new content in a lot of areas, such as history and language, that are very broad and deep. But topics like physics and mathematics are largely moribund, because there's only so much that can be talked about at the roughly high-school level that most people can follow.

So it does look increasingly like Yahoo Answers, but there's still good content if you know where to look. It earned a very good reputation early and that high rep still has some carryover.