I use mine all the time. Reheating coffee when it's gone cold, heating soup one mug at a time and the occasional ready meal. I'd find it very difficult without one. I don't ever actually cook in it though.
I have a combi one - but don't use a fraction of what it can do. Usually used for heating milk for my Horlicks, defrosting stuff I've forgotten to take out of the freezer the night before, and occasionally starting off a jacket potato lol
I always start jacket potatoes in the microwave then crisp them in the oven, apart from the rare bit of reheating, the only other thing I heat up is baked beans, I call my microwave my 'baked bean cooker'.