Google AdWord's Gordon Zhu explains more:

We believe offering a cost-per-view video ad model is good for everyone: consumers choose ads that are more relevant to them; you more precisely find the audiences you want; and content creators continue to fund great content with an ad experience that is less intrusive. Our experience with Promoted Videos, which you buy on a cost-per-click basis, shows that viewers will choose to watch ads that are relevant and engaging.

Throughout testing the "view-through" rates were encouraging with rates between 20 and 70 percent. Advertisers like it because they only pay if the user doesn't hit the skip' button, which could mean that the people who do watch their ads are more interested in what is being advertised.

The new ad format is available in the U.S. and Canada, and is currently in the testing phase in the U.K.

Google has not shared specifics on the pricing model, but it's likely to be similar to Quality Score for search ads. Advertisers who make ads that are skipped less often " or that are chosen by viewers more often " will enjoy a lower price per view.

At this stage, TrueView is not replacing the old, unskippable ads altogether.

As I'm sure you could guess from the very beginning of this post, I get very annoyed with ads that play before a video on YouTube. I'm happy for ads to appear on the left, right, top or bottom of a page, but I think it goes a bit far when it obstructs the very reason for me visiting that particular page. So, I am certainly happy to see the arrival of TrueView ads " thanks Google.