Just for your information:

I have a kernel with options NTP and have been using ntpdate=YES in 
/etc/rc.conf. This made my clock jump around (you can't call that "drift")
and overall degraded system stability in massive ways. Network was unreliable
and at various places I got crashes involving calls to microtime().

Simply switching that ntpdate=YES back to NO made the system incredible 
reliable.


Martin