CO2 is good -I started using it 3 seasons ago, used it several times. On my Tarmac I don't carry a pump - just 2 CO2 charges.
However - for distance riding - particularly in the dark territory - I only carry my trusty road morph.

CO2 alone let me down once when I had a series of flats which exhausted my supply, that day I got a ride back to the car.