Yeah, the fact that he can't make himself finish off Scissors, in spite of all his tough guy talk, and that he can't even WATCH makes Ren a lot more interesting. And after that you factor in his relationship with Yui, and specially once you know she's not HIS girl (Eri indeed hasn't come into the picture at this point) you realize that what's underneath the exterior is something else entirely.

The thing with Shinji, and how rewatching after knowing other stuff makes you see new things... it really makes me want to go and rewatch all the others. orz

(But you're right, it's probably best after a few months' distance)