One of the things that often gets overlooked when building web apps is design.  And there is often confusion about design and what that means.  In fact application design enters into the realm of “Usability”.  E.g. what type of interfaces will make the applications as easy to understand and pleasing to the user as possible.  Great usability design will have an impact on support, adoption, productivity, etc.  When you think great design and usability you usually think Apple – just ask Bill Gates (remember that whole saga with Windows…).  If your assembling a team or selecting a company for complex application development, make sure design and usability doesn’t get lost in the shuffle.