They're mercifully short, but you get hit with about three per episode (marked by the little white lines in the timeline), though you have a limited ability to jump around the ep to sorta avoid them. Still, they're less intrusive than the pop-ups that assault you at AllSP.com or the like. Which is probably a big part of why they're doing this—the online audience for South Park is huge, with lots of sites streaming eps and major torrent traffic. So why not get a slice of that ad revenue?
Ads are going to be a part of any free TV online equation, unfortunately. So are rights issues—for some reason the Britney ep is already available, but the first episode of the current season won't be up until April. WTF? But all in all, they get it as right as an official channel can for the time being, which looks startlingly like a glimpse at the future of TV. Update: Another reason living in Canada sucks: No access for Canadians. [South Park Studios]