...make sure that you specify the blog's minimum PR before submitting an "opportunity". I just submitted one an hour ago, wasn't thinking, didn't mention a minimum PageRank requirement, and right away have 3/4 of the bloggings used up with absolute s**t blogs that aren't even google cached or remotely related to the topic at hand. I know I get what I deserve, but just a word of advice for anyone else that wants to use the service and doesn't feel like wasting $300 like I just did: make sure you list some decent blog requirements!
I am sharing my experience with a PayPerPost opportunity at: http://forums.digitalpoint.com/showthread.php?t=221152 The results are still coming in, but one thing I have taken away from my test is that I am going to be more specific on the type of blogs I am interested in. Half of my blog postings were from PR3's and up. That tells me I could have had all of my postings on PR3+ sites, it would have just taken a little longer. The other thing that I didn't consider, as it gets later in the evening in the US, my opportunity started to get picked up by a few overseas bloggers with mixed results.