My SS1's titanium, to go along with my titanium reg.
It breathes ok, although it feels a little clumsy to bring to my face compared to the octo on my Sherwood reg.
I was looking to save weight and streamline my gear, and the SS1 works well for that.
I personally opt for more weight on the gear. If you dive with gear that is a little heavier, then you do not have to put tons of weight into your pockets or onto your belt. Besides, we are talking a difference of maybe a pound. If your luggage was only one pound away from a surcharge, then you are bringing too much stuff anyway.