Wordbiker

The reason there aren't more disc brakes on bikes in general = Stodginess.

Bicyclists are a very traditional crowd and "unfamiliar" technology like discs really throws a lot of folks for a loop. Once you work with them, see the advantages and learn the very little needed to maintain them, you'll use them everywhere they make sense.

For mountainbikes they are a Godsend. I raced DH on discs and can't see how you could do without them. The increased control, power and modulation once mastered will make you a better and faster rider in any discipline.

For racing bikes...no, there's no real advantage considering that braking is so sparse.

For commuter bikes...definitely nice in all weather conditions, heat or cold and may be easier to deal with regarding removing and installing the wheel.

For touring bikes...maybe not. Since discs are still a specialty item for road bikes (700c) you may not find support out on the road, though you may not need it.