I use Schrader valves. I'm a bit ham-fisted & they've always been kinda bulletproof for me. the inflator works fine. when I screw the cartridge on I don't hear any pop when it punctures the canister. I grasp it firmly & press it on the valve firmly & squarely. with Schrader valves I have to support the valve from the other side, pressing on the tire. which doesn't block the air. as soon as it inflates (which is almost instantaneously!) I take it off & test the pressure, either with a pinch or a gauge. if it needs more, I just press it on again. there's nothing to fuss with, screw the cartridge on & press against the valve. bingo bango I'm riding again

the cartridges come in diff. sizes

it was particularly useful one time when I had a slow leak. I was able to occasionally boost the inflation as I finished my ride. so convenient!

as cyccommute mentioned, the spring tension is tight. in fact, I thought my first unit got worse or wasn't fitting right, so I bought a 2nd & carry both. but they both work. they are tiny so I have to keep them in separate plastic zip bags, in my field repair bag, to be sure I don't lose them. 1 is by itself & 1 is w/ 2 cartridges

on epic rides I sometimes carry 4 cartridges in addition to my pump

on at least 1 occasion, I had 1 new cartridge be a dud. brand new, screwed it on, no gas. unscrewed it, no gas escape & it had a new hole from the inflator. I imagine new cartridge duds are quite rare but still, if you're gonna carry 1 you might as well carry 2

cartridges don't work when frozen so I keep them in my house during winter & carry them with me when I go out. they don't go in the winter bag they go in a coat pocket close to my body to stay at least a reasonable temperature

I also carry a small hand pump

you might want to test using it at home the next time you're swapping tires or something, so you have a feel for it. especially if you're using Presta valves, I think