Sure, Bills had some big, highlight reel hits, but his coverage was suspect. Too often he went for those bigs hits when he could have come away with a few picks if he were a step faster reacting to the pass. He often got caught out of position and got beat over the top (see the Boise State game last year).
I expect Nacua to continue to improve and we will nit miss Bills at all.
As for Takenaka, he has potential to be very good. However, at this point we just haven't seen enough of him to know if he'll be able to step in well for PoVey.