I bought the "Giant" one and have had to use it quite a few times and had no problems with it. Plus it does not use all its CO2 up once you disconnect from the tyre like some do, so if you puncture again, there is still some gas left to pump your tyre up again and still hard enough to ride. But over time I have found that a used cartridge that has been left in the inflator does loose its CO2. I do not know what pressure it pumps up to but I find it makes the tyres rock hard on my road bike so suspect it is well over 100lbs+ as advertised.
But dispite having a CO2 inflator, its still advisable to carry your pump in case you have multiple punctures and use up all your cannisters, or as in the case of my ride just recently a slow puncture where you can just keep giving it 50 - 100 strokes to keep the tyre rideable. So long as you don't have a stupid grin with your eyes shut on your face when your stroking, nobody will think otherwise.
Also recommendable is the Lezne inflators, I searched all over in the LBS for the Giant and Lezyne ones, and then found a LBS that stocked both, so it was a hard decision to choose which one.