I have made a little more than $14 on Ad-sense so far. Its not much - but it is something! However, I have it linked up in my booksforteensreviews.blogspot.com blog, my knittingstuff.com website, and my westernsaddleblankets.com website. My blog for books has something like 140 followers I think.
It depends a lot on what topic of adds google places on your blog. For example...1 click on an certain add can earn you $20, were 1 click on another add topic can earn you a mere $1.
I say go for it - however, I suggest only doing the small 1 box adds because if you have a large stream of adds along the sidebar of your blog, it can turn of your readers. Experiment and see what amount works for you!
I've been doing adsense for about 2 years and made maybe $200. Not a great return, but things have picked up a lot now that my blog is getting more traffic. I have about 200 followers. I agree. Give it a shot.