I installed this recently on my BMW R1150Gs and it looks great. I only installed the low beam, as I don't want to wait for the high beam to warm up when I need to flash someone.
I ordered the 4500k 55w bulb. The light is a nice color - it's not as blue as a stock HID from an Audi or BMW car (those are probably 5,500 or 6,000k).
Looking into the light - it's white. Looking at the output it's close to the color of sunlight (white - slight yellow tinge).
Installation was a snap. Plug and play - though there were no directions. I had to modify the cap that seals the enclosure for the headlight because the HID bulb is longer than the stock halogen bulb.
I do notice with the bike engine off a slight hum from the ballast - but once the bike is on, it's imperceptible.
I'm not sure without side by side testing and pictures, but it appears that due to the length of the HID bulb (the glass part) the light may be focused on a different part of the reflector than a standard halogen bulb, causing the dispersion of the beam to be slightly stronger on the sides of the road than straight down the center. This can be looked at though as a good thing - generally, I don't need as much light down the center because of overhead street lighting. I can always use more light on the side for turning. Plus once you throw your high beam on -- you've got all the light you need down straight.
