I did the same conversion on mine. While I appreciate the increase in lumens for less wattage, I'm not thrilled with the dispersion pattern, since the HID bulb is not located in the same place in the stock reflector as the H4.
I'm now considering finding some sort of LED headlight for which I can make a bezel and fit in the stock housing without the reflector. LED seems to be more efficient than even HID and a factory unit should focus much better.
I've been browsing the Clearwater and JW Speaker offerings.