Trying to get benchmark data...
What would you consider a good CTR for...
1. Text ads
2. banners ads
...on the display network?
Internet Avg. is .04% for text-links and .12% for 300x250 banners
CTR Performance Guide for 300x250 Banners
.05% - .1% CTR == Bad
.12 CTR == Internet Average
.2% - .4% == Very Good
>.4 == Your micro-targeting. In one niche I'm seeing 10% CTR's on textlinks(!) on certain exact-match URLs.
I would generally stick to CPC advertising on Google, it seems setup better that way. I've tried transitioning some campaigns over from a CPC to a CPM campaign, but never seem to be able to replicate the same impression volume.