We have been living without a microwave for a few months now. I still have our microwave but it's in the laundry room. When we first made the switch it was hard. I had to plan ahead for reheating leftovers or thawing out meat.
If I am reheating meatloaf, lasagna, or some other casserole I just put it in the oven at about 300 for about 10-15 minutes. If I'm reheating soups I just put them on the stove top. I also melt butter in the stove in a oven proof bowl.
The biggest adjustment is definitely remembering to start thawing meat the night before and to put your leftovers in the oven in a timely fashion so they're ready for lunch. My whole family agrees that our food tastes much better since giving up the microwave.
We only use the microwave now for the timer, making homemade popcorn, and if my hubby needs to reheat something quickly for his lunch.