Not long ago, a lot of people were posting that their earnings had gone up significantly for a short period.
I stopped using co-op when google started slapping affiliated sites ... I am still an active member of Link Vault though, and have seen great benefits to my sites. You just need to put a bit of thought into how you build your links. Remember that organic link building requires both reciprocated and non-reciprocated links.
I have >400 impressions and 0 clicks On the other revenue sharing forum: 800 impressions and also 0 clicks