As JenSense reports while I was away, Yahoo Publisher Network checks being sent this week. I noticed my account balance has depleted, but the checks screen shows nothing in that window - hence, still in beta. However, many others at WebmasterWorld forums noticed the total balance screen dropping as well for them. It is good to be in company. This probably is directly related to the payments being sent.
I will let you know when/if I receive the check.