Is WikiAnswers a good site?
It can be useful because it is likely that somewhere someone who goes on wikianswers will know the answer to your question and type it up however that is also one of its weaknesses, because any one can put an answer up they may lie or get it wrong. There are supervisors and Vandal patrol that try not to let that happen though.
The other thing about it is that you are part of a HUGE network of people who are trying to help each other by answering questions. It can be very nice to be a part of a community that has chosen to be together to do something positive!
It all depends. Generally, WikiAnswers is a great site to find answers to your questions. However, anyone can answer questions, which means that sometimes the answers are biased, rude, or just plain incorrect. There are Supervisors for this reason. Supers are in charge of specific categories and watch over them. They edit answers that are incorrect or need to be grammatically changed. They get rid of answers only when the answer is wrong or is irrelevant. So, with the help of knowledgeable Supervisors, WikiAnswers is a great place for answers and advice.
Yes, WikiAnswers is a very good site. Anyone can ask and/or answer a question. It has a large category tree, so pretty much any question you may have may already exist and already be answered.