If you read the media kit (on the lower right hand side) It has a demographic outlay that specifies not only the break down of the visitors but also the kind of products most often advertised on the site (or at least what products their viewers are most interested in)
I often see health niche products offered on the site as well as a slew of political products (online newsletters, etc.) So it seems, from my observation, anyone in the health and wellness niche and political niches, could fare well from the traffic.
You have to submit a query to get a rate card. I havent received anything yet but I am certain its based on a CPM rate. The articles I have seen imply that the rates are actually pretty modest
How would you rate this with regard to its potential for effective advertising for IM