I like the idea of wikipedia, and I'll use it the way Force Flow mentioned: quick lookups for something. Some areas I am willing to trust because I can see the quality of the editors (chemistry, medicine (depending), computer science, typography) while other pages I read knowing at least half of it is total bunk.
So long as 12-year-olds can throw in "Joe is gay!" into any article (which is only annoying really because you know right away that it's just online graffitti) and so long as people with personal agendas, vendettas, or whatever continue to insert either false information or, what I find much much worse, false summaries from real sources (how often have I gone to the study myself only to see, clearly at the bottom, the researchers coming to completely different conclusions than the Wikipedia editor) which are harder to detect. Trying to verify some of the information online doesn't always help: lots of other sites copy content from Wikipedia (and that's fine when they state that, and a date, but often they don't).
So, I do use it, I used to be a contributing editor there (nowadays I'll still fix typos and grammatical junk under my ip still), but I don't donate and we're actually looking into buying a nice set of paper, edited by pros, modern set of encyclopedias. It's nice to be able to look something up in a book and know that not only was it vetted by a smaller group of people, but with modern internets, they can even have an errata page if you suspect there's an error and you can confirm it.
I still have a huge Physician's Desk Reference, as well as some books like Hole's Anatomy and an old Taber's medical dictionary which I've used back when I edited Wikipedia. Even though books may (will) have errors, I feel safer using them as my basis for important, everyday facts. For every good editor and good admin over there, there are plenty of people who are determined to make Wikipedia state "The Truth".
I'm also not donating because I do not like the idea of real journalists using Wikipedia as their main source (why do they do this? All the "real" sources are conveniantly listed at the bottom of the article) and I don't feel that donation is going to improve the value of the articles or help spread the word that Wikipedia is a convenience and not a one-stop for any research of any importance. I donated my time there once, that's it : )