Just an update. I picked up the ABV have used it just once. I was a little worried because it sits low compared to the Guardian, but I didnt have any problems with water making its way in. I shore dive, and usually have to swim 200-300 yards to my drop point, so the ABV helps a ton. very simple to open and close, and installed very easily. I think its a bit overpriced for what it is, but it does save gas on those long surface swims.
Going to use it a bit more and give more detailed thoughts later.
On another note, what regulator setup are you all using with the Sprectrum? I use my g260 and the weight of the reg pulls on the mask a bit. might get another setup dedicated only for use with the Spectrum moving forward.