The Bella parisiacae urbis of Abbo of Saint-Germain-des-Prés gives a really good indication of the Parisian response to viking raids in the 9th century. Nirmal Dass put out a translation of it in the Dallas Medieval Texts and Translations series in 2007. The long and short of it is that they were marauding pagans against whom the Christian Parisians were the sole bulwark, and their savagery knew no bounds.

This, of course, is an exaggeration and misrepresentation of the way Scandinavians actually were, but vikings were, by nature of their career-choice, not exactly the nicest of guys.

Balts and Slavs probably held the vikings and their culture in high esteem, since archeological evidence points to the fact that lords of Slavic and Baltic gorods often allowed scandinavian traders and merchants to settle there, viking art and craftwork were appreciated, copied and bought, and several slavic states hired viking mercenaries.

While combat archeology provides examples of viking vs slav warfare, it was not more common than slav on slav warfare. It is fair to say that the relationship between Vikings, Slavs, and Balts was rather that of trade, cooperation and mutual curiosity than animosity.