I have always used my blackburn track pump to both pump up my tyres and monitor the pressure but because it features a small analogue gauge without too much detail precision was far from perfect. My normal routine consists of pumping up tyres slightly over a thin line marking 20psi with the next indication on the gauge being 30psi.
Having said that, that is how i have setup my bikes pre riding for the past 1.5 years now and have grown accustomed to it. Recently trying to fill up a $100 wiggle order for free shipping i tacked on this little gadget. The packaging is minimal and so are the instructions. I found the operation of this unit fairly confusing. Whilst the on/off/bar/psi and led backlight was simple enough to figure out it took a fair bit of time to figure out how to actually measure the air.
Like many pumps it is hard to figure out when you have a secure lock on the valve itself. I used to plug the unit in and get all sorts of weird readings from 7psi to 40psi etc etc and made the unit highly untrustworthy. It wasn't until recently that i realised that you basically have to push it down very firmly right down to the bottom for it to get the proper pressure reading and even if you do this sometimes you get some bogus reading from the unit not engaging the valve properly. However i would call this satisfactory. Not as good as 100% reading every time but certainly usable unlike the start.
Once i realised how to operate the unit properly i was getting a few surprises. I pumped up my tyres as per normal and inserted the sks airchecker to check the pressure. What i thought was my normal operating pressure of around 20psi-25psi front-back turned out to be something closer to 32psi up front and 36psi in the rear!!?? Now i knew the gauge on the pump was inaccurate but i wasn't expecting this. This difference in perception and actual pressure is huge and sure to make a difference on any trail. The unit itself has a button which allows release of air from the valve without removing it but you do need to remove the unit and plug it back into the valve to reread the new pressure.
I have now being on a couple of rides where the pressure is set correctly to my preferences and i can honestly say combined with tubeless and no fear of running lower pressure it has definitely provided a performance benefit. For people that are quite clinical with their bike setups and take pride in maximising performance this relatively cheap tool will take the guess work out of finding the right pressure for your riding and then maintaining that pressure for subsequent rides.
Cliff notes :: A useful tool that has a few minor niggle but definitely worthwhile especially considering the cheap price.