Was listening to a panel on startups yesterday (I'll highlight these in another post) at Supernova2007. One of the panelists was Paul Kedrosky. When asked what he looked for in a company his answer was "companies with ideas that appeal to my innate laziness"
I think it's an excellent point and I would add to it. If there's a task that occurs everyday in your life, people will always seek ways to either shorten the task or make it more pleasurable. If you can provide a product that does either of these two things you have a shot at success. If you do both well (and have good marketing) you will have great success.