I would love to be able to use multiple roles per user. I’d like to be able to have a number of different groups of capabilities — such as creating and managing blog posts, creating and managing pages, other custom post types, moderating forums (I’m using buddypress) and so on, each group of capabilities corresponding to a responsibility on the site. And then I’d like to be able to assign one or more responsibilities to a user. At the moment I have to define a separate role for each possible combination of responsibilities.