As mega said you need to add all users to a sorted set called users:reputation.
So go through all your users and add their user ids to users:reputation with the score being their reputation.
@bentael Did you get ba chance to beat on that Drupal dump I sent ya?
@Shard not yet man, I've been busy trying to solve memory issues in the importer core. But I will very soon. in the next 2-3 weeks hopefully. so far I got these exporters to implement, Drupal is 2nd on the priority list after Wordpress
Any chance in the mean time?