I ordered this cordless inflator after midnight and it was delivered by 7p. Hats off to Amazon for Out of the box I had to charge the battery for about 3 hours before getting the green light.
It took 11 minutes to inflate a completely flat car tire from 5psi to 40psi. That's a lot longer than my plug-in compressor would take, and it got pretty hot by the time it was done, but this cordless inflator is a lot more convenient to use, and it's not as loud. It had enough juice left to add 4psi to each of the other three car tires with battery to spare. When I was done it took about 5 hours to recharge the battery.
It has an LCD screen that's makes it easy to read the pressures. You can set the pressure you want to inflate to, put the inflator on the ground, and wait for it to auto-stop when it reaches the pressure you want.
I found it inflated 0.5 to 1 psi higher than the setting, but that's ok. You want some wiggle room to lose some air when you pull it off the valve, and test the pressure with an analog gauge.
I also prefer the clamp-on attachment to the valve over the screw-on attachments. The clamp is quicker, easier, you don't lose much air removing it, and fingers don't get dirty.
It has its own LED light that would come in handy in the dark, a car power adapter if you have to plug in on the road, gloves to handle the inflator when it's hot, attachments to inflate balls, toys, etc, and a carrying case to put it all in.
Overall, this is a great choice for maintaining tire pressures and other small jobs.

The Oasser air compressor is a very handy tool for inflating bike and even car tires. I decided to replace a plugin air compressor with this battery air compressor for better convenience. The battery allows this to be used anywhere, since it doesn't need to be tethered to a car. It is also easy to use since it has a straightforward button layout. The air compressor automatically stops once the set pressure is reached. Also it doesn't take very long to fill tires and is quieter than the plugin air compressor that I have been using.

The air compressor is around the size of an electric drill, meaning it is fairly small. But it isn't small enough to be practical for being carried in a backpack. The exterior of the air compressor is mostly made from plastic and has a rubber grip that feels nice in the hands. The hose is a good length and has an extra extension hose for making it compatible with car air valve tires. The led is surprisingly bright and stays on when the air compressor is on, not just when the trigger is pressed. The top of the air compressor does get hot after extended use. I would recommend letting it sit before removing the hose from the body of the compressor.

The item cost me a bit of money, so I expected a higher level of quality. The carry case is very thin and has very thin and cheap packaging plastic to hold the pump, battery and accessories. There's an accessories chamber on the pump where special hose attachments are stored, but the door is cheap and doesn't easily stay closed, nor does it lock in place. The hose itself is tricky to screw onto a Schraeder valve. Cheap gloves are provided, because the air hose is supposed to get very hot and so you're supposed to put on the gloves before unscrewing it. You have to unscrew the air hose to put the pump back in the case. I especially don't like the little light at the front, which turns on whenever the pump is on, using up the battery even when the pump is at rest, and cannot be shut off without turning off the entire unit. A simple switch on the light would have solved this problem.

That said, the pump works fine, and is very lightweight and convenient. It looks mainly like it was designed as an emergency pump for a car. For a bicycle with 20" tires, the unit does the job quickly and easily - once you manage to get the hose screwed on. I had no problem with the battery duration, nor did the hose warm up during the short time I used it. Not as robust as my plug-in portable air compressor (which was cheaper than this), but it's nice to use battery power and not have to find an outlet for a power cord. I would have preferred some better engineering and quality control on the device, but I'm generally happy with my purchase.

The item cost me a bit of money, so I expected a higher level of quality. The carry case is very thin and has very thin and cheap packaging plastic to hold the pump, battery and accessories. There's an accessories chamber on the pump where special hose attachments are stored, but the door is cheap and doesn't easily stay closed, nor does it lock in place. The hose itself is tricky to screw onto a Schraeder valve. Cheap gloves are provided, because the air hose is supposed to get very hot and so you're supposed to put on the gloves before unscrewing it. You have to unscrew the air hose to put the pump back in the case. I especially don't like the little light at the front, which turns on whenever the pump is on, using up the battery even when the pump is at rest, and cannot be shut off without turning off the entire unit. A simple switch on the light would have solved this problem.

That said, the pump works fine, and is very lightweight and convenient. It looks mainly like it was designed as an emergency pump for a car. For a bicycle with 20" tires, the unit does the job quickly and easily - once you manage to get the hose screwed on. I had no problem with the battery duration, nor did the hose warm up during the short time I used it. Not as robust as my plug-in portable air compressor (which was cheaper than this), but it's nice to use battery power and not have to find an outlet for a power cord. I would have preferred some better engineering and quality control on the device, but I'm generally happy with my purchase.

I've used this rechargeable inflator for several months and have grown to love it. Just set the pressure and pull the lockable trigger. The unit shuts off when it reaches the chosen pressure.
The pressure indicated on the gauge is fairly accurate (compared with another gauge of know accuracy).
The rechargeable Li-on battery holds plenty of juice for inflating even a large tire. It comes with a lighter plug, but the wire is definitely on the short side. Get an extension wire for lighter plug-ins if you intend to carry the inflator in a car.
It is slow, so the best use is for topping off tire pressures as opposed to filling from scratch.