The HIDs are a very cost effective solution. Best bang for the buck. The only disadvantage is that they can take a little while to come back up to full power if you are going back to low beam for oncoming traffic then back to high beam. If done within say 20 to 30 seconds hardly any lag, and even in startup phase the HIDs are equal to or are better than the standard H4 high beams.
The other disadvantage is that standard headlights will never be good enough again! Some H4s +100 or +120 make things more bearable from the headlight, but a pair of those bulbs cost nearly as much as the HID driving lights.
I rode with someone else who had what looked like the setup I have on the ST1100, looks exactly like the link Abe posted, but startup time was noticeably less on his. Mine were a few years older, so perhaps tha ballasts are better now.
