I don't know if any of you have experienced this, but one of my HID bulbs turned really purple and then burned out after ~2.5 years and ~55k miles, so I had to replace both bulbs since the one that was still good was a noticeably different color than the new one.
(Sharp HID 35w 5000k, daytime running lights NOT disabled)
Also, the holes that I had to cut through the plastic caps behind the lights to feed the HID bulb wires through were allowing a bit of moisture into the headlight housings through the rubber grommets that were supposed to seal them completely, so I had to remove both headlight assemblies from the car and bake them in an oven to dry them out really well and then use some silicone to seal up the space between the rubber gromets and the plastic caps... at that point I probably should have just done a retrofit.
I agree, a retrofit is certainly the best way to go, but in my opinion, the stock 06/07 WRX projector headlight housings aren't nearly as bad as some other cars that I've seen with extremely glarey aftermarket HID kits (older Civics and Scion TCs with reflector housings immediately come to mind).
07 WRX (Albins 5MT + Blouch 20G)
Jorge Carrillo Tuned (365 whp/340 wtq)