I kinda like the slider idea. There's no need for me to see the extreme options, it's enough to reason about whether the default case applies - if not I can play around with the slider. Exploration versus direct information is an interesting UI aspect I haven't really given much thought until now. Too much of the former and your UI looses discoverability (e.g. Office Ribbons). Too much of the latter and you overload your users with information (e.g. Eclipse Toolbar).