Lavinia, unless you have money to burn it's probably best to stay away.
The way they are set up seems to be totally at odds with how any normal person would search online. They try and impose their own categories on to people.
I had an online discussion with them on behalf of a client who signed orders to the tune of £ 6,500.
When I complained about ads not showing, they said searchers were "searching in the wrong category". When I told them people searched by keyword so the ads should show regardless, they just kept repeating their answer. He cancelled his order.
We also tested some banner ads with them. We found they did not display if the searcher used Internet Explorer (which 80% of the customers did at that time!).