The anime is starting Shikamaru's transformation in to a complete bad ass. While not a whole lot actually goes on in this episode, it's still pretty good story-wise. Really, this is how all slow downs should occur as to prevent boredom.
We really don't know much about Rinnegan though. I used to think that it let Pain control his bodies, but with the thing about the chakra antennae being revieled, that doesn't seem to be it. So I'd say except for the lore about the first ninja guy, we know absolutely nothing about the Rinnegan.
Also, it's the Byakugan that can tell normal clones from real people, but not clones that split chakra like shadow clones, and probably the other elemental type clones.