If you have basically no idea what you're doing, or just want an example for something, it can be great.
On the other hand, if you try to find an answer about something you're really knowledgeable about, the result is often unsatisfactory:
Like trying to find the reference documentation to answer some specific question, and the documentation is buried under a lot of SO questions (that usually don't answer that question).[1]
Or you find someone who asked exactly the question you're looking for an answer to, but it either: has no answer, despite being very old, or has been closed due to being "not constructive" or "off topic".
[1]: While I generally prefer the in-language documentation, e.g. Python's integrated documentation is often missing notices (deprecation notices, warnings about illogical behaviour, ...) that exist in the web version.