Essentially, the Bold 9780 takes the existing Bold design and adds the BlackBerry 6 OS first seen on the touch-screen, slide-out BlackBerry Torch. I've been a happy user of the Torch since it appeared, but I must admit that I don't use the touch screen very often -- for most tasks, a keyboard/pointer combo still works better for me. As such, I can see a niche for the 9780 to fill.
BlackBerry developer RIM says that the device will be available through local carriers. A quick scan of current Australian BlackBerry providers didn't show up any specific 9780 deals yet, but it seems reasonable to assume most higher-priced cap plans will include the phone as an option once the telcos got over their Christmas rush.