I've been happy with my LED's in all turn signals and rear brake lights. I have the ones from SuperBrighetLEDs, 45 SMD. Turn signals were a bit problematic for the rear. I wanted the amber color for the rear turn signals, but the red lens just took the intensity down too much. Not too bad for at night, but on a bright day they were not all that noticeable. Switched those out for the same red ones and illumination was MUCH better and stuck with that. The amber LED's up front work just fine.
It is interesting to note that the coding appears to modify the timing of illumination for turn signals. While the cycle is still 1Hz (500ms on, 500ms off, repeat), when in LED mode through programming it's more like 400ms on, 600ms off, repeat). This matches the side repeater as well (which is already LED).
2013 X3 28i (prem, tech, cold1&2, conv, hud)