In my humble opinion, all of you make some interesting points. Well considered. In the end, I have to agree with ReefHound. A conscientious diver should have a good, firm feeling of how much air is in the tank, even if a SPG does crap out!
I own a Gekko. The only reason I didn't buy a Cobra is $$$. Having said that, I also prefer (just personal preference) an analog SPG. I am not making making any statements about the resolution or accuracy of either. I just prefer the human readable interface (HRI) of an analog gage. One of these days, I am still going to buy that Cobra though. I like gadgets.
I am more concerned about this whole discussion on the 'battery crapping out'. Who let's this happen? If my battery meter starts reading 50%, I start looking for the nearest convenient opportunity to visit my LDS and replace that thing! I have even been known to replace a perfectly 'charged' battery just because I was going on vacation and didn't want to chance the battery dying mid-way through my vacation. This despite the fact that my battery meter read 75% or better. Come on guys! Replace that battery at appropriate intervals whether it needs replacin' or not and the battery won't be an issue.
Like ScubaTexasTony, I too carry a HP hose and analog gage in the bag, just in case.
Peace. Y'all have fun divin'