I like that it is easy to create ads, but sometimes you have to pay for more features than what we need at first glance! It's not always clear how much they will charge us if things are unclear in their terms of service or pricing page (I think this happens quite often).
That said though - once your set up correctly with templates etc., then everything runs smoothly & efficiently from there onwards. We've been able to produce some brilliant looking adverts within minutes rather than hours/days as before our old system took ages when using multiple images / colours per advert.