Born2dive - All the Zeagle Reg's have the feature. The question you should ask yourself is does my throat feel chapped or raw from breathing dry air. If your throat feels normal it's working. To answer your question I dive with a 50D and the moisture provided isn't noticeable the lack of a dry throat is.

Mel - good point about the carbon filter. I heard of people experiencing bad air fills. That alone may interest me. Of course some of the divers out there are smoking 1/2 a pack of cigarettes on the boat on the way out to a dive. I don't think they are too concerned with air purity or lung damage.