We are currently running a test of Vibrant intext ads. Vibrant works similarly to Kontera. We will only be running the Vibrant ads in the HubPages share of impressions on hubs that have Kontera enabled (in place of Kontera).
i have to agree. whenever i stumble upon articles on the web that have them, i stop reading because i feel it is just a 'land mine' of keywords, and i felt that way before HubPages. too distracting, which is why i don't use Kontera ads on my hubs.
Same with Kontera. You don't really get good results unless you have high traffic volume. In most cases, they don't benefit you. That's probably going to be the same with all contextual ads.
The only thing I'd like to see in a contextual ad is that they're relevant to the page. Kontera pulls a keyword say 'grass' in a hub about feeding tortoises, and puts an ad about dead grass or something random to the keyword.