Well, I have manufacture installed ones and running on them since summer of 2007. Had to open right headlight unit and purchased 1 oem (Philips, $134/each) before I cross referenced them. (yes, I deserve some names). So after dicking around when headlight unit pulled out, I've heard some wonderfull stories how to bake-owen the unit to certain degree and take it apart to repair/replace damaged/crambled off insulation off the cables. The story was pretty creepy, so I took heatgun and opened by steps. took apart, replaced all the wiring, straighned edges as "prettyfull" and functional asI could, use some clear RV and clamped the unit together. new lamp installed and ballast cross-references with left unit as working one.
One thing is crappy - leveling is not working for both now. I think I either pinched or screwed some wiring in that little connector that hooks to inside leveling motor.
The light is working so far for 2 years. Seems to be sealed ok. I still wonder if anyone bakeowen headlight unit to separate, though.
I'll definitely go with matching bulbs and ballasts. I've seen fellows with chinese kits in 5-6 month lifespan.