graeme_p - 8:03 am on Jul 1, 2011 (gmt 0)
Just to update this a few months on. I went with Vibrant and they are producing about 30% of Google earnings most months, with no discernible impact on Google earnings.
I am now moving on to trying affiliate links, to further reduce my dependence on Google.
@Shatner, my experience of Infolinks was lots of very low quality ads and negligible earnings.