I'll give you my impressions of what is going on with two of my sites. These aren't tested but rough stats and some figures that are in my head.
Discount Shopping UK - By far the highest ctrs come from the text links. I tested a while back and found "Click here to visit ....." in big lettering providing the best ctr. Just had a quick count up (from the affiliate marketing companies) and the site's had 116 reported click outs on affiliate links from 410 uv's so far today (US day). About 25 of these are banner clicks, the rest are text clicks. So I'm getting around 20% CTR on the text links "click here"
Digital TV - First thing I'll say is that I've deliberately made it a "bit plastered in ads", the site gets some very targetted traffic from people looking to spend money on TV services.
Adsense (so far this month):
post page top 1,032 impressions ctr 2.81%
sidebar top right 1,135 impressions ctr 1.76%
The banners get clicked, but the majority of the sales for Sky Digital come from the text links and not the banners. The sales from Setanta, 1-3 per day, come from mainly banner ads.
I know it's not very scientific or accurate but it should give you an idea of what's going on with those two sites. But, like you, I get a higher CTR on text ads (discount shopping uk), I deliberately took the banners out of the post pages (it's WordPress) apart from a few selected top right banners... and at the end of the day it's all about those legitimate small, flat baked biscuits
