The dedicated programs do a better job, especially if they come with profiles for your particular camera. Often doing it yourself rather than using a profile, especially if only applying noise reduction to a masked off part of a shot, is better. However, while for a one off shot that's fine if you have many then something like noise ninja using profiles run as part of a batch or action does a much better job than CS4 built in noise functions.
Try downloading a trial of Define 2 from Nik Sofware and see what you are missing.
Another vote for Noiseware.
Mind you, even that is all but redundant on images from the D700!