Sometimes yes, sometimes no.
I personally like it, because alot of the information is linked to (on the well done topic/subject pages), and further information is only several (at most) clicks away.
That said, I always keep in mind that it is written by people, and people are prone to flaws.
But any other source would have the same against it, really.
It's just that Wikipedia (and other online/electronic sources) are easier to manipulate than paper.