I am fairly new to the whole brewing experience, but I would probably be inclined to say not to use a wooden barrel for primary fermentation.
This is going to be a lot harder to clean than plastic or glass due to the number of gaps in the wood! My main theory is based on the idea that you are discouraged from using a wooden spoon for stiring your wort.
I may be wrong but I would say don't do it! You would probably be okay in secondary since there will be more alcohol and this will be more tolerant to bacteria. Don't take my word for it!
Despite what everybody says, you could always take the option of try it to see what happens. You never know you might like the results. I would only do this if you are willing to ruin an entire batch though!!! Could be worth the gamble :D