I withdrew a non-negligible amount of USD from TradeHill by simply filling out a form on the site and clicking submit. The resulting page said that they would put a check in the mail that same business day. Apparently they did! Because that was only last Thursday, if I recall correctly, and the check arrived today.
So this is just a report for anyone who wants to know that there was no delay, confusion or extra steps.
Here's my TradeHill referral code. So far I've made about $0.50 in referral bonuses, so it isn't so much that I hope to make a lot of money by passing out my referral code, but it does give you 10% off of their normal fees if you sign up with it:
https://tradehill.com/?r=TH-R11149Regards,
Zooko