Moonlights are really great for the health and sanity of your fish, in my opinion and experience. It really brings out the noctornal behavior of many species, and it makes for a wicked night-light if you keep your tank in your room! :wink:
Corals also have different behavioral patterns when exposed to the frequency of light that is moonlight, and many inverts come out or do things under moonlight that they just dont do "in the dark".
I have two moonlights built into my lighting fixture, a Custom Sea Life 2x65-Watt PC fixture in its own aluminum housing.
For what its worth, getting a moonlight setup would be both aesthetically and practically a smart move, helping the dynamics of your reef ecosystem. Also, try and get the ones that are external or after-market, because the ones that come built into fixtures are not replaceable, and when they start to crap out, thats it (Im having that problem right now, actually...).
Good luck, though, and make up your own mind! :wink: