[Zordrack]

The light emitting part of an LED is neither the same shape nor in the same location as the filament in a regular halogen bulb.

And since angle of departure is the same as angle of incidence the light will not be focused and directed correctly in a reflector made for halogens.

Personally I don't worry about that unless it's for headlights (high/low/fog) where beam pattern is really crucial.

But don't expect to get "correct" beam pattern out of a reflector light made for halogen with LEDs in it.