My wife and I normally carpool since we both work downtown, but last week we had to drive separately (one of us had to leave work early). She drove behind me in our Explorer Sport with the drop in HID kit in the Lo/Hi beam projectors. Never once when she was riding my tail, a ways behind, or going over a speedbump did I feel like I got flashed in my mirror from her headlights. The car I was driving is a sedan, and sits much lower to the ground than the Explorer. I've also passed her heading the opposite direction before, and didn't feel blinded at any point.
The drop in kits in THIS headlight don't blind anyone. Perhaps you are thinking of older style all reflector housings (which DO look terrible when having HIDs added), or people who drive with their fog lights on all the time (who have a special place in hell regardless of whether they use HIDs or halogen)?
edit because you replied as I was typing to Tony:
A very small number of users on this forum (and the moderator) believe you shouldn't install HIDs at all unless you buy expensive new lenses and reflectors. They're right that the full upgrade looks better than stock, including better than the Ford HIDs in the Limited, but the drop in kits are more than adequate. The kits are a fantastic value if you don't want to pay for the expensive conversion, and are willing to settle for something that looks completely stock to all outside observers, because its what the Explorer should have come with.