I live alone, and still find the dishwasher to be the most useful appliance in my house. I cook a lot, and love not having to think about how many pots/pans/dishes I'll use and how I have to scrub them later. I don't do any prewash either. Everything goes straight into the dishwasher and comes out sparkling every time. Maybe I'm just really lucky with my machine/detergent.
It's also great because I don't need extra space for a drying rack.
As a single person I preferred the laundromat. I could use 3-6 machines at a time and everything was done fast. I owned enough cloths for a full load of each, and so I only had to do this once a month.
As a married person with family we are doing laundry all the time anyway and so having it in the house is an advantage.
It's also great because I don't need extra space for a drying rack.