Some more points for (and against) leaf shutters:

They're cheaper than focal plane shutters. Fixed lens cameras almost always have leaf shutters. But with interchangable lenses, it's cheaper to build one shutter, in the body, than one in every lens. That's why there are so few interchangable lens leaf shutters in 35mm, and those there are almost all have the leaf shutter and rear elements fixed to the body, only the front elements interchange, limiting lens design freedom immensely. It's also a pain to build the mechanical linkage allowing the body to cock the lens.

Bigger than 35mm the expense, physical shock and sync limitations of focal plane shutters are much magnified, so there are many interchangable-lens leaf-shutter systems.

They require much less force/time to cock. Leaf shutters have for decades been used in MF SLRs where the shutter is open for viewing, closes when the button is pressed, reopened for exposure after the mirror is up, closed after exposure, and then opened again for viewing after the mirror is back down. FP shutters don't need to do this on an analog camera because they're behind the mirror, which is good, because they can't be re-cocked quickly enough.

The problem arises on digital cameras where one wants continuous viewing on the LCD monitor. None of the FP-shuttered digitals (all the interchangable lens ones) can use the LCD as a viewfinder--thus, ironically, this useful feature is found on even the cheapest digicams, but it's missing on the expensive ones.

The cocking force issue also led to a special breed of leaf shutter: the Press shutter. These shutters are cocked just before use by the force of triggering them.

Against them, it seems they are much more prone to needing a CLA once or twice during their life; FP shutters are more likely to work fine right up to their final demise.