FWIW I like the KISS principle. I either have enough gas for the dive or I dont... (dive). I have an o2 gauge, as diving an Inspo with a standard case, button gauges are a pain for checking between dives. The o2 gauge is there for convenience, but it is short and I cannot easily see it underwater. I have car 'blind-spot' mirrors on each of my wrists should I relly feel the need but, really, it's because I have a compelling fetish for a clear chest
I do have one for the dil that I can see (but it is either tucked down with the BC hose under my arm and across my front or clipped off a la DIR). It is there as sometimes I use the inboard as bailout on shallow dives. Otherwise I wouldn't bother.
Anyway, Inspo divers have 2 perfectly good o2 gauges without a HP gauge... the handsets! Works for me.
EDIT: I had a HP gauge fly across a carpark once. Nasty. I would prefer button gauges really.