Man, so much air drill hate around here!
I have 12v, 18v & corded drills, but would still go for my air drill most of the time working in the truck shop (drilling frames for boxes, replacing fenders, drilling out rivets, etc). If it's a tight spot, you already have an air hose, and you know you're going to be there for a while, they are 10x better than holding a 18v battery over your head until your arm starts to fall asleep.
That said, I had an older IR 3/8 that worked great, but upgraded to a used reversible 3/8 Matco (not sure if IR or CP era) that has been a big improvement. Matco Model number is MT1789. There are a couple on ebay right now averaging under $60 used. For 1/2", I used a coworkers' MT1727 with the handle, and it was just a bigger version of mine. Both are made in Japan, parts are readily available online.
Reversible is the way to go, from bits getting stuck to reverse threaded bits, it is just a big help when you need it. I added an air regulator to the intake so I could slow it down and not burn up my step bits.
I would never hesitate to buy one used, just open up with an adjustable wrench, pull out the rotor, wipe down and check the vanes & barrel. Wipe off and throw some grease on the planetary gears, and if the bearings are smooth just toss it back together.