Usually yes, and I trust it as far as informal knowledge. For example, if my Maths course did essays (thank Gods we don't), then I wouldn't use it as a reference, but for informal knowledge gathering I do trust it. My reasoning being thus. Anything non-academic is likely to be unimportant (unless it's news, in which case I use the BBC website), and thus it won't matter too much if there are a few discrepancies as long as the general article is correct. Anything academic is only going to be written by people who understand the subject in question and thus is extremely likely to be correct, even if it is unintelligible to us mere mortals. And thus anything can be trusted on Wikipedia. The only problem is vandalism, which is only likely on the non-important stuff (anyone vandalising pages on quantum physics, for example, is simply sad and needs to get a life), so it's always worth checking other sources. But on the whole, I definitely trust Wikipedia.