FWIW, I display instantaneous power on my Garmin. You get used to reading what you display and yes the numbers jump around. But that's the nature of power data and it's not like you're looking at the power readings continuously,

My coach was the one who suggested instant power, because you really don't want to know what you were doing 3 seconds ago, you want to know what's happening right now. And you want to learn to be smooth.

I'm not saying any one is right or wrong- there's different ways to display the data because people have different schools of thought. Just providing a counterpoint to the "3 second" comments- because not everyone actually does that and at least some of us who don't have a sound rationale behind their decision.