I have been running a successful ringtones campaign using search. I decided to expand the campaign to the content network, so far I got 1057 clicks - 1 conversion I used the same ad I used for the search network.
you kind of answered your own question, you have a conversion. you just need to tweak your ads, landing pages, keywords, merchant choice.
One of my campaigns converts better on content than search, and better on myspace than any other site.
As far as tweaking your content ad, you should definitely look at excluding sites that have a large number of impressions/clicks and no conversions. The people seeing ads in the content network are not 'buyers' or in 'buying mode' in the majority of cases. So you will likely need to tweak your ad copy to try and appeal to only those in buying mode... and not those expecting it to be free who click because it appeals to them.