I, too, bought the HID's from Chad and they are awesome. I have to say, it's one of those things you would not think is that great an upgrade until you do it. I kind of thought it would be a mostly-appearance thing, but they have made a world of difference in night time driveability. Now that I have them, I would never think to be without them. Not only is the path of the beam intensely more visible, you'll also notice things like street signs way off on the sides lit up like it was daytime.
I don't have a lot of upgrades, but this is by far the best time and money I've spent so far, excluding drivers schools!
I was able to mount my ballast and igniters fully inside the stock headlamp housing, which is great. No drilling, loss of housing seal, etc.