I've just started using Chitika Premium on one of my other blogs Authentic Greek Recipes. The initial indications are good and I find it a great complement to AdSense.
Chitika doesn't contravene the AdSense T&C as it works in a different way. It pays per click, but appears only to those who have come to your site via search engines and shows ads that are related to your search terms. This means that you have to have a decent percentage of your visitors coming through search engines, otherwise it's pretty pointless having it. Also, at the moment it is only for visitors from the USA and Canada. So anybody visiting you from outside of that area doesn't even see the ad box.
So if you have what you would consider a decent number of people visiting your site through search engines and from North America, then I would say it's definitely worth your while signing up at Chitika. They approve (or disapprove) your site pretty quickly and if you have other blogs, you don't need to reapply for each of them - they are automatically included in the initial approval.
Once you have done that, then make sure that you get the optimum size and placement of ad box. I have placed it above the blog posts so that it can be seen immediately on 'arrival'.