Does anyone have any good stats as to the usefulness of product videos? e.g. “Prospects are X% more likely to convert after viewing a product video”?

So videos, in general, have been a great asset for moving prospects through the funnel. Having used Vidyard in the past for product videos and on-demand webinars, I have seen more than 60% of prospects in current opportunities viewing the videos as part of the lead lifecycle. 

In some cases, they viewed right before an opportunity was created, while a bigger portion has been when they are past 50% of the opportunity lifecycle.

This is mostly true for products that have a long sales cycle, like around 6 to 12 months. As @James Winter mentioned Wistia, Vidyard will have more industry benchmarks on this.

I can connect you to my contact at Vidyard if you need more details on this. 

I don't have any off the top of my head but you might be able to find some published stats in the content produced by Wistia or Vidyard. we're implementing vidyard to be able to see exactly what those metrics are since it has a great marketo integration.