MERCURY-FREE D3S/D3R and D4S/D4R HID bulbs

What is the hype with the "new" D3S/D3R and D4S/D4R HID bulbs? These new type of bulbs will look identical to current D1S/D1R and D2S/D2R HID bulbs except they will be Mercury free, to meet the  environmental priorities of both manufacturers and consumers while conforming to all international specifications.  D4 type and the equivalent Mercury containing D2 type will need compatible ballasts to operate.