I'd go with a york-style setup before electric - can be costly though.
I went with CO2 and love it. Last time I went out I aired my tires down to around 8 PSI. It took me longer to remove the valve-stem caps and plug on my fourway airsplitter than it did to fill them. 300+PSI at 45CFM = fast fills.
BUT, like you said, when the tank's empty, it's empty, then you're F'd. I keep my spare a little over-aired up just incase. Then I can split it's 35PSI into my other tires.