Size of the tank is fine, but its really about the horsepower of the motor and amount of air motor can put out so that you don't have long period of motor running in order to build a pressure in the tank.
Great General Purpose Portable Compressor - I bought this compressor to run nail guns, air sand and spray paint.) The tank pressure gauge is just behind it.

The main panel has a working pressure gauge with a pressure adjustment knob next to it. This regulates the pressure that reaches the hoses, not the tank pressure. If you work at lower pressures, the unit will not cycle as often. It is also handy to limit the pressure to safe levels for your various air tools. It is not as loud as large upright compressors, but it does make a fair amount of noise, although not as much as I expected. I use it with a Souix air sander and it does run longer when I am working. I don't think it would keep up with two continuous flow tools. If you take on a tractor trailer, get a bigger compressor.
Excellent compressor - quietest I've used in its category - I am never able to live without a good air compressor. I use them for a variety of tasks from simple blowing to nailers and air hammers. As smaller air compressors go, this one really delivers a nice, steady pressure for quite a long time.

Normally I like to blow through my air gun at about 50psi to clear sawdust. Blowing air at that pressure really drains a small compressor fast, but this one really handles it well and gives me quite a bit of extra time due to the fact that the motor really kicks in quickly and efficiently to keep the pressure up.

I couldn't outpace the compressor with a single nailer.

The two air ports is really nice in one this size because I can put the compressor underneath my workbench and mount a static line on my workbench for easy access anytime while leaving the other open for longer hoses. These size compressors can make an INCREDIBLE amount of noise, but the Porter-Cable 3hp 4 gallon side stack really keeps the noise level at a minimum.
Plenty of Power to Offer...but it needs plenty, too. - I tried the compressor on an
undedicated 15 amp circuit, and it immediately blew the switch every
time.
I also learned (the hard way, of course) that if you are using the
compressor with a 50' extension chord (with too high a guage) on a 20
amp circuit, the pump will not get enough electricity to pump air
after cutting-in when the tank pressure drops to 110 psi (the
specified cut-in pressure) - the pump will start pumping, but quickly
stop and you'll hear the motor straining until it blows the 20 amp
circuit, too. It's
cheaper, my new Porter Cable friends say, to buy more air hose than
the right gauge extention chord - Ah, such knowledge I'm gaining.
Sadly, the compressor arrived with an air intake filter housing badly
bent downward (done apparently at the factory, as the box from Amazon
wasn't damaged), so I couldn't remove the air filter. AND, the drain
valve (to drain water from the bottom of the tank) would not
completely close allowing lots of air to excape from the tank. In my
chats with an Amazon tool sales rep, and later with a Porter Cable
tech rep (to help me unravel the compressor's electrical-needs
mysteries), both Companies quickly and nicely insisted on sending me a
new air intake filter housing and a new drain valve (I guess I'm
getting two of each?) - no questions asked. The machine is fairly
loud, but it only takes my pump about 6 seconds to refill the tanks
from the 110 psi cut-in pressure to the specified 135 psi cut-out
pressure. I figure the noise level goes hand-in-hand with the added
power this compressor offers - power I think I need.
Frustrated with the technical assistance -
I received my compressor and unpack it. When I turn it on, the tank pressure gauge wasn't working. I went there with the compressor and they took it and said to leave it there for one day, and on the next day they should call me to pick it up. But, after 3 days, they still didn't have changed the little tank pressure gauge, and they said "we are waiting for Porter Cable to send this piece to us, you have to wait until next week". Ohhh! Come on!!!
I can't believe that! The most common and cheap part of a compressor they don't have in stock!?
Is that kind of technical assistance we have from Porter Cable when we just buy a brand new compressor and need it working???
I think I should send it back and bought another from another company, because, now, I'm just waiting and I can't do my job.
almost perfect - Love that it kicks in at 110 psi or so which keeps the pressure always high.
Great buy - Size of the tank is fine, but its really about the horsepower of the motor and amount of air motor can put out so that you don't have long period of motor running in order to build a pressure in the tank.
Darn Good Little Compressor - Short and sweet - this compressor delivers on its promises - it is easy to use, easy to break-in, easy to maintain, and you can't beat the duel air hose inlets. I have found both of the built in pressure gauges to be accurate, and the oil-free motor is quieter than other compressors I have used (although it still makes a good bit of noise). To me, that's portable - I can understand how that would not be the case with everyone, but my experience leads me to believe that this compressor has a very good weight-to-horsepower-to-air storage capacity ratio.
This Portable Compressor is Rugged and Well Built ! - Surprised and impressed! I looked at Home Depot and Lowes and decided to order this air compressor to save the Tax and the trouble of bring it home.

Looking at the other brands of portable compressors I really like how well this one is built.

It has a sturdy cage that protects the Tubing, Regulator, pressure switch, and brass connectors.
Fantastic Compressor - I do crafts and wanted a compressor to replace my old one when it died. I was told by others that none of these smaller compressors would do that. It drove my Porter Cable narrow crown stapler with long runs before having to build more pressure. No problem ! ! ! I could get most of the nuts off of one tire before the compressor would come on again. Perhaps this compressor wouldn't do for a mechanic, but for someone who changes their own tires, it does just fine. It is noisy, but I don't think any more so than any other compressor.
Better than the pancake model - I've used the smaller Porter-Cable pancake compressor for about 2 years. The only thing I don't think is an improvement is the knob for adjusting air pressure.

This time I installed the compressor with the air hose reel from Amazon mounted right beside it on the floor. If you get the reel, you'll probably need to make a trip to the local hardware store for an interconnecting piece to connect the reel to the compressor.
Don't know yet - I received a unit with a defective pressure switch which cuts out at 120 PSI instead of 135 PSI. When I called three days later to follow up, they then refused to take the unit back and replace it with a new one. I spoke with the owner of the company, Kim Allen, and he said that I would need to have it repaired under the warranty. After several calls to the toll-free number in the manual to the factory, I was put in touch with a repair facility an hour away and was told they don't stock the part but could order it and get it back to me in a few days. Hopefully, PC will come though without me spending four round trip hours and a week without a compressor.