Rodd, the HIDs take about 10 to 20 secs to full brightness. Once on the same bulb is used for hi and lo (a magnetic thing pulls the bulb in and out), so instantaneous between hi/lo. The delay time for driving lights unless you can leave them on for a while is what is holding me back from converting my spots, as conventional bulbs are good for places where you are going on and off all the time. LEDs may be the go here once they improve a bit more and come down in price.
The modification to the base of the bulbs is the same as for using a normal H4. One of the original bulb plugs is used to trigger the HIDs, but both are still there if a normal bulb has to be used. The HID wiring is in parallel to the orginal wiring (it comes with its own relay loom and plugs for the bulbs and ballasts). The plastic that has to be removed is the screen and the panels that are over the headlights so you can get access in there. Removing the side pocket makes it easier to route the wirng back to the battery. The ballasts can be located on top of the headligt or off to each side using ties. I believe the ABS models have extra gear around there so it is a tighter fit. A ground wire is need to go up to the ballast area. What I did was run a ground wire to one of the bolts on the back of the instruments and use that as a common ground pole for the ballasts. The power wire extended on the relay (best to do this while not connected up ion the bike.
Just think about the wiring as having to do the same as for installing driving lights and their separate relay. The power circuit is common, as is the ground circuit if you use a common ground. Each HID bulb has its own ballast, so if one goes the other should still work unless it is one of the common circuits that have gone.