those risks are about the ntp protocol, not the service / firewall port. ntpdate is just as "vulnerable", but no, it's really not a realistic concern, given the benefits of proper time sync.
In fact... you're MORE at risk using ntpdate instead of ntpd. as ntpdate just uses a single shot to sync time, if you hit a dodgy server, you will set the wrong time. ntpd will use 3, 4, 5 or more servers meaning the service will identify any individual sources which are apparently defective compared to the signals from the others, and reject them.
Last edited by acid_kewpie; 01-09-2013 at 03:19 AM.