The controller will allow you to add the additional feature of having the low beam litronics swivel up 5 degrees when you turn on the highbeams to help the high beams fill in more space, for a better light spread. It is a good feature, but I havn't added the controller because I rarely even need to use the high beams anyway as the low beam litronics alone are usually plenty enough light for me anyway. You still will have high beams without adding the controller, but just that the low beams won't swivel up to help them, they just stay pointed at same level while the high beam is turned on.
When I had the plain halogens, I used to always turn on my fog lights as well when I drove at night because I felt the low beams alone didn't give me enough light, but with the litronics, I don't need to put the fogs on ever...unless there's really fog.
Hope that helps.