I have released version 1.55 of nsdiff, which creates an nsupdate script from differences between DNS zone files.
There are not many changes to nsdiff itself: the only notable change is support for non-standard port numbers.
The important new thing is nspatch, which is an error-checking wrapper around `nsdiff | nsupdate`. To be friendly when running from cron, nspatch only produces output when it fails. It can also retry an update if it happens to lose a race against concurrent updates e.g. due to DNSSEC signing activity.
You can read the documentation and download the source from the nsdiff home page.
My Mac insists that I should call it nstiff...