I'm a one-person household and have a combination microwave/fan-oven/grill counter top thing from Sanyo.
Sometimes I use one function, sometimes a combination, but I would certainly miss it if it died. My conventional oven & cooktop do get used, but much less than if I hadn't the Sanyo.
Re-heat direct from frozen is easy, so I tend to cook for 4 or 6, freezing the extra for future use.
Despite having it about 10 years I am still finding new ways to use it. For instance I recently found that the baked potato (combined micro & fan oven) setting will cook a beetroot nicely too. Tell it the weight and it does the sums to make an easy result with just the serving dish to wash afterwards.
I had a normal microwave before, which I liked too, but the combi is much more versatile, and (for me at least) well worth the extra.