The ads are triggered when a visitor leaves your domain by clicking on an external link on your site. They are not triggered when the browser or tab is closed (these are not pop ups), when you move within the domain, or if you open a link to a new tab or browser. You also have the ability to exclude exit links if you like. I did not want an ad being shown if someone is going to my accounts like Google+, Twitter, or my RSS feed, so I am excluding them.
You are also allowed to adjust the timeout and background opacity to make your ads as unobtrusive as you like or conversely to drive more revenue.
The reporting is simple, but has everything you need to track your performance and earnings. All payments are made via PayPal. I would think both of these areas would become more robust in time.
A sample ad with my settings:
It will be interesting to see the engagement (clicks) over the nest couple days. For you web analytics people, I have asked them if the referring website on the site the user is clicking to will show as the true originating domain or the GapAd network (app.gapad.net). As soon as I know I will update the post.
Update: Ian Clarke, Co-Founder of GapAd, replied to my question:
That is a good question.
Currently the referrer will be GapAd, as the referrer passed to the destination website is determined by the visitor's browser.
Our engineers are investigating whether there is a way to pass the original website's URL through to the destination site, to ensure that the destination website's analytics are accurate.
Please don't hesitate to let me know if you have any additional questions,