Wikipedia is surprisingly accurate, and it generally self-corrects very quickly. It's great for a quick answer if the user is mature enough to use it properly and cautiously. Wikipedia is even better at providing references, as all of its entries should be sourced. So it can be a great place to start, but not necessarily to finish.
So, for example, if one looks up the Battle of Gettysburg on Wikipedia, they will find an extremely detailed and accurate article on the topic (i am looking at this now). At the bottom of this article, they will find a long list of references, many of them written by experts and peer-reviewed, which one can follow up on independently. Obviously, if one were writing a college-level paper on the subject, then they would use the references rather than the Wikipedia article itself as source.
I agree that some people throw Wikipedia in your face as if they are experts, and they should do their research much more carefully. James Wales, founder of Wikipedia, has agreed that people should be more fastidious in selecting their sources. However, if you just need a quickie understanding of, say, what happened on the third day of the Battle of Gettysburg, Wikipedia can be a big help.