Some of it is very good. I have a couple wiki articles on information theory and radio signal coding printed up and on my desk right now. They are very thorough and have great reference lists for more research. If you are writing a school paper, read the wiki article and then use the references to research further and to be the actual sources. Hey, those are the same rules I had in school for paper encyclopedias - read it and use it for a first step in finding the original sources.
Wikipedia is and always has been full of stuff mixed with poop.