Their marketing angle seems to be that they provide more control than Adsense or YPN in whether a page uses their contextual engine or preset keywords the publisher uses. They also have some publisher-friendly statementes about not wanting to erode publisher brands, which is all well and good, but I don’t think it’s clear yet why they won’t be eroding brands. They state they won’t have strings attached such as the pay-per-call ads that can appear in Adsense.
I like competition and choice for publishers, so I hope Miva does well. However, they’ve been trying to establish themselves more in the PPC program for a long time and haven’t been able to really make much ground on Adwords and Yahoo Search Marketing. And as we’ve seen with contextual networks, publishers number one concern is revenue, and you need lots of advertisers paying lots of money to make contextual work well. Can Miva deliver enough advertisers to cover niches well? Yahoo has struggled to match Adsense for publishers due to less contextually relevant ads. It seems like Miva would have a harder time than Yahoo.