I don't think I would bother in order to sell a house - I would de-clutter madly, paint everything cream, and make sure everything was clean as a new pin; but for myself I would love the chance to hire the services of a designer.
I'm assuming that they would work with me to decide what I wanted to keep, how we use the house, what our tastes and budget are etc, rather than just imposing a design on us.
I once saw a TV series where people didn't want to move, but felt that they didn't have enough space. The TV company sent in professional de-clutterers to see what could be disposed of/thinned out, then architects/interior designers to create storage and/or design features that would work for the lifestyles of the families and the style of the house. It only ran for one series, unfortunately, but it was really good. I remember one woman had something like 6 fish slices, and a dozen tablespoons
. She hadn't realised until they were all laid out for her to see.
The storage ideas were so clever, too. If I could afford it, I would love to have something like that done, but I'm guessing that the cost of de-clutterers, designers, builders and decorators would be way above my budget!