For now it's possible to have pagination only based on elements. It would be really helpful to have a pager for grouping as well.
Let's say we have 100 nodes, each node tagged with 1 of 5 terms from 1 vocabulary. Then we group those nodes by their term. Now under navigation option there shall be the possibility to page the results by a given number of groups. For example 1 group per page, so that now we have 5 pages, and every element of that group on one single page.