There are 2 of us and we have a half size one.
We run it once a day, occasionally there are bits we cant fit in and they get left to one side for the next run.
The day where we'd tend to have the most amount of stuff would be a sunday, breakfast pots/pans/dishes, sunday roast and associated pots/pans/dishes, and I do tend to hand wash a couple of pots rather than leave them to one side.
I think it also depends on your cookware, I use cast iron pans so they would never be going into a dishwasher anyway.
One thing I do find is that its hard to fit large items in, like a roasting tray, and would sometimes handwash rather than use up all that space. Also wine glasses do not fit anywhere so I hand wash those as well.
If I had the space I would probably get a full size one, but it would mean getting more dishes/cups etc..and I dont have space for those either!!!