I find myself on the fence about it all the time. I don't use it for cooking, but I do use it for food prep. Mostly we use it to warm up leftovers quickly (30 seconds and you're good to go!) I also use it for some quick defrosting (like frozen fruit for smoothies) and occasionally to pre-cook vegetables before I use them in my cooking.
So could I get rid of it? I've heard that reheating on the stove or in the toaster oven is just as easy, almost as quick, and usually results in better tasting left-overs. It just uses an extra pot or tray, since you can just throw your plate into the microwave. Defrosting is a little tougher, I think. I don't often remember at 8 in the morning to take out that chicken, and sometimes I don't even know that I'll feel like a fruit smoothie later in the afternoon. Pre-cooking the vegetables would be easy; I just need to get used to taking the extra step on the stove.
The other thing that drives me nuts is the space it takes up. I have a very small kitchen, and space is at a premium. Right now the microwave is on a stand that houses linens, laundry on one shelf below, and flour and potatoes on the bottom shelf. So the space is multipurpose. But it does make that wall a little squeezy to get around the table.
So the microwave will be one of the bigger quandaries I'll consider when I do my huge house purge and re-organization this summer. Maybe I'll try putting it in the garage for a couple of months and see how it goes.