Depends on the food, but for most meals we prepare at home up to half the items are done in the microwave and half using traditional cooking methods. For instance, we buy some vegetables frozen in single portion sealed plastic steamer bags. We just put them in the microwave for the 2 minutes or so recommended, and get really fresh-tasting corn, peas, Brussels sprouts, etc. Not soggy that way at all. Perfect amount for the 2 of us, no leftovers, no pots to clean, quick & easy.
We also do baked potatoes in the microwave, and fresh corn on the cob (wrapped in plastic with butter inside). For my teapot I microwave water in a glass measuring cup I use just for that purpose. I have an accessory for cooking eggs, from soft to hard, that works really well. No need to watch the water and mind the time, you just enter it, and hard boiled eggs done this way (up to 4 at a time) are the easiest to peel I've ever done.
Naturally we reheat some leftovers, but not all. Most Chinese food we like is usually good that way, but pizza I prefer in the countertop toaster/oven, to keep the crust crisp. The microwave is the only way to warm tea or coffee that's gone cold, right in the same cup.
Also when my husband makes some soup in a very large stew pot, and it later goes into the refrigerator to serve us for upwards of a week, I'll ladle some into a soup bowl for perfect microwave reheating anytime I get hungry. He does a great chicken soup for when one of us catches a cold, or mostly in my case when I frequently dehydrate, and I swear it really is a magical cure.
And so while my late parents were like the elderly couple that pellaz mentions, not even ever owning a microwave, this elderly RJ couple uses one every day for all kinds of tasks. We simply can't function without one.