Easily one of the better $20 investments I've made in my bikes.
Since all of my tires are tubeless, and I cycle between riding my bikes, sometimes several days will go by between rides on a particular one. What I find frustrating on my pump (Bontrager dual pump for both HP and HV tires) is that attaching and detaching the pump often results in significant air loss. With the JACO, there's almost no loss of pressure at attachment or detachment, what little there is, it's just a small fraction of what happens with the floor pump. This lets me check my air pressure quickly, and if it's within the desired range, I know it will still be there even when I detach it.
Also the bleed valve is cool because, as I mentioned with the Bontrager pump, if I want to pump something up to 65psi, I have to overshoot it by a bit and hope that it's a clean detachment, otherwise I may bleed out more air than intended. With the JACO, if I slightly overshoot the PSI with the pump, I can accurately bleed it down to exactly where I want it, knowing the JACO only loses a tiny amount of air.
For those who are interested in buying, there is a warning on the Amazon page that this is intended for higher pressures up to 160psi, "if you want 60psi or less you should buy the 60psi version". The problem there is that the 60psi version maxes at that pressure. So if you're like me and have a gravel bike you run at 45, and road bikes you run at 65 or higher, it seems you have to buy both. You don't. This measures my gravel bike tires just fine and lines up well with the Bontrager measurement (within 1psi of each other) whether I'm doing the gravel or road tires. Maybe at sub-60 psi the other device is more accurate, or has finer measurement gradations, but I find this to be good enough for all my tires. Now if you are a MTBer perhaps the lower psi model makes sense...since I' m not I can't speak to that.