In defense of oil-less compressors:
Of course sensible compressor sizing is important, and they're not as long-lived, but they have their place.
On a per-CFM basis they're expensive, but if you just need a little air, then the low buy-in cost is worthwhile.
One way they are great is if you need air without any hydrocarbons in it; for medical or food-handling uses. It's very simple: If you have oil in your compressor, then you will have oil in your air; if only a trace. With an oil-less compressor you don't need to consider HC removal when planning your filtration system.
Heat is the enemy: Compressing a gas increases its temperature; don't run higher pressures then necessary; it's also more efficient.
Many oil-less compressors have a run-in procedure. RTFM if you want to get the most out of it.
I see a few of you guys run nailers. Here's a tip:
I did some work for a construction company a couple of years back and when they needed to borrow a compressor of mine, we got to talking about their compressed air issues.
They usually kept their compressors wherever they first got power to the site and would run hoses wherever air was needed. They found that their nailers didn't run so well at the end of a long run. With the intermittent demand of their nailers the solution that worked for them was to put a remote air receiver on whatever level they were working on.
Any appliance that takes air in gulps and appears to be starved will be better served by having a secondary receiver nearby.