I have one now, but I didn’t for about 8 years. The only reason I have one now is because it came with my apartment; if there wasn’t one there already, I wouldn’t have bothered buying one. I really just use it to melt butter, where it’s a bit easier than doing it on the stovetop. The only leftovers I ever have around are pizza, and that tastes so much better when it’s reheated in the oven or on the stove…
good for reheating and small portion cooking.
also good for shorter time cooking and summertime cooking. you can bake a potato in 4 minutes and it doesn’t heat the kitchen so much.
you save on cooking costs when you don’t need to heat a whole oven for a single item or two. you save on cooling costs in summer by putting less heat into the house. money saving and energy conserving.
I would trade my microwave for a dishwasher in a heartbeat, if I could only figure out where the heck the dishwasher could fit in my kitchen, without seriously redoing all the cabinetry.
Well, those two aren’t mutually exclusive. Plus, if you cook, don’t you ever freeze your leftovers? I know that my use of leftovers has become more efficient since getting the microwave. Before, I’d leave stuff in my freezer for over a year, because I just didn’t feel like dirtying a pot, waiting 15 minutes for it to melt and cook, etc. So a lot of stuff would get freezer burnt and thrown out. Now, 4-5 minutes in the zapper. No mess.
Anyhow, the oven is also good for those who like to cook. Steamed vegetables are, in my opinion, better cooked in the microwave than stovetop. Looking online, it apparently isn’t just my opinion. From Mark Bittman:
I have a microwave and love to cook but I don’t cook in the microwave. I use it for reheating leftovers (I am big on portion things into containers and freeze) and for making breakfast oatmeal.
My microwave is part of my GE Advantium oven that does convection and halogen cooking too. It works better and faster than heating up my electric oven, which seems to take forever.
I love my microwave for steaming veggies, or reheating leftovers, melting butter for using in something else. If it were not for me loving to bake, I could make do with a microwave and gas burners.
At one point in time with my first husband when he was doing a passive aggressive whine thing and I had essentially no kitchen, I cooked for 9 people for a month with a microwave and a single gas burner, and a toaster oven. I used the rotissery on the grill for pretty much most of the meat. We did roast chicken, roast pork loins, roast leg of lamb, spit roasted hunk of beef. I fell back on a fair number of medieval recipes that were designed to be cooked in pots of water, over coals in a spider, or spit roasted. Not insurmountable, but I made everybody else wash the dishes =)
We have 3 and they all get used with some regularity. Had a countertop model, then we moved into a place with 2 kitchens and each had one. When one went out recently we brought the countertop back in until it could be replaced as it easily sees use 2 or 3 times a day. We don’t “cook” with it per se but it does “assist” with lots of reheating, melting, popping, defrosting, etc.
I’d hate to be without one, just for coffee alone.
Coffee left on the burner too long, or reheated on the burner, tastes crappy. Best way is to turn off the coffeepot right after it’s finished brewing. And then if you want a cup later, nuke it - it’ll taste much better than if you reheated it (or kept it warm) by conventional means.
Oh, look, another thing that Dopers can turn their snooty noses up at. 
I do not have a microwave; I have TWO microwaves (I don’t use the one in the basement - I’m keeping it to put in the media room once we have one). I use the one in the kitchen almost every day; I would miss it terribly if I didn’t have one.
Sure, I freeze a lot. But I don’t freeze whole meals. Things I do freeze are: sauces (especially pasta sauces that take a lot of time), soups, bread dough, fresh pasta etc. But there really isn’t a good way to heat those things mixed together (except maybe for frozen pizza with toppings, but even those usually turn out slightly disappointing).
Of course, some of these things, especially the sauces, are probably quicker to reheat in a microwave than anything else.
Seeing so many people praising steamed/microwaved veggies does make me think. I’ve never tried it. I don’t really steam veggies much, and a microwave could make the process very easy & quick.
This is me! I probably wouldn’t starve to death, though, I’d just eat out almost exclusively.
I cook only vegetables and meat I’ve either grown or killed with my bare hands using tools whittled and smelted from ore I dug up from the ground, directly over a fire of redwood and mahogany.
And Twinkies, microwaved for seven seconds on high. God, those things are delicious.
No microwave, but more because we have no space in our tiny kitchen for one. I’ve gotten used to it, I suppose, but it’s still damn inconvenient.
You bastard! You can’t burn redwood and mahogany! I only cook using renewable bamboo.
I know my kids will not starve, as long as they have a microwave.
We have had one for ages.
However, the one thing we don’t use it for is popcorn.
Still do that the old fashioned way on the stove - just tastes better and seem to have more control over it.
BTW, my classic stupid story:
Washing my toothbrush, I thought a good way to get rid of bacteria would be to zap it in the microwave. Seemed logical at the time.
Put my toothbrush in the microwave for about 2 minutes.
My toothbrush came out cylindrical - looking like the world’s tiniest toilet brush.
I didn’t grow up with one, and I certainly know my way around a kitchen, but I do appreciate the microwave and will probably always have one.
Edit to add: I bought my first microwave for five dollars at a thrift store. It didn’t work, and that was fine; it was GIGANTIC, and I used it to store my shoes in 
I have a set of microwave cookware; I steam fish and vegetables for dinner on a regular basis. The food is moist and delicious and clean up is easy. I find that I get a higher volume of scrambled eggs cooked in the microwave than on the stove.
Wow, I figured it would be 100% that people had microwaves. Hard to imagine life without one. Especially since they are so ridiculously cheap these days.
I remember in the 80’s paying over 300 bucks for a Litton. It lasted 20 years. My new Panasonic was only $150.
Funny how tough those Littons were. I’ve talked with several people that got twenty or more years out of them. Mine still worked, except the keypad started freezing up. I’d have to unplug it to get it reset. It finally reached a point where I bought a new one.