I just noticed that where-as before the old busybox binary went into /opt, it is now being left in /bin.

Is there a reason for this, or just a side-effect of using dpkg's divert mechanism on it? (I don't know how dpkg diversion work, but if it's possible to put it in opt, I think that would be more ideal, except for the rare cases when busybox-power breaks boot... except we know it doesn't, and anyone arguing for that on those grounds is making a silly claim, because hundreds of users boot on a regular basis with busybox-power as their busybox and no errors have ever surfaced as a result; not to mention you extensively test things.)