I'm sure that a good number of people have requirements that OpenNTPD can't satisfy. However, for most home or office users I'm sure it's good enough.
E.g. here's my OpenBSD firewall, which syncs to a number of NTP servers on the net (including pool.ntp.org and time.apple.com):
$ rdate -npv clock.isc.org
Fri Dec 19 18:23:11 PST 2014
rdate: adjust local clock by 0.012466 seconds
And here's an internal OS X desktop running Mountain Lion. It doesn't talk to any NTP servers on the Internet, only to my firewall system running OpenNTPD:
$ ntpdate -qu clock.isc.org
server 149.20.64.28, stratum 1, offset 0.011798, delay 0.05516
19 Dec 18:24:43 ntpdate[2000]: adjust time server 149.20.64.28 offset 0.011798 sec
$ ntpq -p
remote refid st t when poll reach delay offset jitter
==============================================================================
*xxxxx.yyyyyyyy. 4.2.2.3 4 u 307 512 377 0.223 5.384 2.611
Being synced to within 12 milliseconds of a reliable stratum 1 NTP server is good enough for me. NB: I don't normally use clock.isc.org, there are plenty of stratum 2 and higher servers available for use.
E.g. here's my OpenBSD firewall, which syncs to a number of NTP servers on the net (including pool.ntp.org and time.apple.com):
And here's an internal OS X desktop running Mountain Lion. It doesn't talk to any NTP servers on the Internet, only to my firewall system running OpenNTPD: Being synced to within 12 milliseconds of a reliable stratum 1 NTP server is good enough for me. NB: I don't normally use clock.isc.org, there are plenty of stratum 2 and higher servers available for use.