Yell has been signed up as the first advertiser. 3 UK advertised for partners in July. It has been successfully run in Austria with advertisers such as Honda, Suzuki and VW (yes, curiously automotive-oriented isn't it).
I'm a 3 subscriber and frequent, often frustrated, user. So I'll keep you posted on what it looks like and what the impact, if any, is on the service.
Oh, and before you ask, "Received Top" of 173.6kbps (on the graphic, left) after 15 mins is actually pretty good for where I live...in Central London.