The team at chrono was very responsive to our needs, they worked well within deadlines we set them (usually sooner than expected) as my business partner had some health problems which meant she needed more time off work! My favourite thing about chrono was their ability to understand what I wanted, even when it wasn't clear from my words or examples of what i'd seen elsewhere.
We used this service to drive traffic to web pages that were part of our website but also linked out via newsletter signups - so there's been no impact in terms of cost per lead/sale generated.