It'd be very interesting. Pagan Rus' would be very much set apart from the rest of Europe. Not that that's really too different from otl, but over time the Rus' kingdom, which may well elevate itself to empire anyway, will remain a strange, exotic, deeply foreign land to Western Europeans. It may have a friendlier relationship with Lithuania, whose pagan rulers would feel under less pressure to convert and thus probably won't (the conversion of Lithuania otl was a pretty unique situation driven by the immense dynastic opportunity presented by Hedwiga of Poland). It would definitely have a huge impact on art and literature, as the mythology of Slavic paganism would be preserved and the great mythic stories would be written down and inspire further works. There'd also be a whole artistic tradition around the building of temples and creation of images of gods.
I think the likelihood of a crusade against the Rus' is unlikely, for the simple reason that Rus' is huge, populous, and lacking in either valuable resources or theological justification, meaning it'd be far too hard for too little gain. If the Slavic pagan religion is consolidated under Vladimir, and has rime to stabilise and become part of people's identity, any crusade would only serve to strengthen that identity, much as the crusades in the near east strengthened Muslim identity in opposition to the Crusaders.
If there's a good, strong theological justification for the Rurikid dynasty's rule, similar to the Chinese concept of the Mandate of Heaven or the Japanese concept of the Emperor's divine descent, it could help stabilise the Rus', especially as any high priesthoods would be most definitely subservient to the Velikiy Knyaz/Tsar, unlike Patriarchs who could sometimes challenge him.