depends on what you really want to do. at one time i ran a ntp daemon on one of my internal boxes, and it worked fine...until the day that all of the pc clocks on my network got hosed because i had to do maintainence on the ntpd box.
i settled for using Dimension 4 for my windows clients:
...and ntpdate, running as a cronjob every fifteen minutes for my linux boxes.
it's easier because now all the machines need is a net connection.