I deal with CPV a lot and run of network is alot less targeted than a URL or Keyword campaign. RON is nice if you have a large budget, and you are able to hang in the game to see what works, because there will be a flood of traffic. It works well with larger markets such as biz opps, grants, insurance etc.. However, If you are on a tight budget then I suggest sticking with either url, or keyword campaigns. Be more specific with the keywords/urls you choose.. yes your traffic will be slow, but you will be able to stay a little longer and expand off of those results..
Make sure you set up a tracking pixel to track EVERYTHING, This is going to be a key element for success.
If you want, PM me and Ill let you in on my rotator that sets a pixel and tracks referrers. Maybe I can help, maybe not... it all depends on your market, how much traffic interest there is in the market, and what urls and keywords you use.
I was going to try to start sort of a advertising co-op a few months back, but never followed through, but I would be glad to give you some advice in cpv.