I've used MIVA PPC. I got a ton of clicks, but little or no sales. They have a wide range of content sites that they automatically post on. You really have to target your ads to a specific niche to get the best traffic for your money. I spent almost $250 because I didn't put limits on my daily spend. You have to do that or Miva will go crazy with clicks that don't result in sales. It was very frustrating. Once I learned how to tame Miva, it worked better. You have to have a good product and specific market to target to. Just be careful that your keywords fit your market and not the general public.
I signed up to Miva and never used them. The reason for this was that I had join each of my sites separately rather than just be able to use one code from a master account for all websites. Outcome: Stayed with Google.
I have used them before. I absolutely hate them. A lot of the keywords that I chose for my site kept getting rejected. So I sent them an email asking why my keywords were getting rejected. They told me that they were not relevant to my site. I insisted that those keywords were but they kept arguing with me. So finally, I decided not to spend a penny more with them.
miva is just useful if you need some uk traffic... They're cheap, but useless for me. same thing happening to me. The expression "london jobs" was also not relevant to a job classifieds website of mine... lol My guess is that you must bid higher to get more clicks at first.