I have a 4300K Kit in my 04 4runner. I use the oe reflector housings and am satisfied with the results. For comparison, use your stock system and project the light onto a white garage from say 5 feet away. You will notice that the reflector housing naturally has stray light as there is no definitive cutoff within the headlight assembly. Your HID Kit will emit more light output (lumens). In turn, there will be more light 'escaping' upwards.
The new projector housings on the 06-07' also have marginal ammounts of light escaping and will have more if a HID kit is installed. (more light output).
Drivers will be annoyed if they are going up a hill, while your traveling down it. Thats just natural, due to the way headlamps are designed (aimed downwards).
I installed my kit using 3M velcro strips that I bought from the Home Depot for $4 (Inner fender wall for the passanger side, and on the side of the battery for the drivers side). The velcro is industrial strength and the kit can be removed relatively quickly. I have oem toyota ballasts, which are quite large, but the velcro is holding them up well.
