Well, I got my pair and have mixed reactions. Mine are the white ones, which are probably a lot less bright than amber or red.

1) It is nowhere near as bright as a 50W halogen for the backup lights.

2) It is a way cool color compared to the halogen, definitely much higher color temp, giving it an eerie xenon look. I really, really like this color. If I could figure out a way to use it in my fog lights instead of the daytona 18w lamps I've got now, I would definitely do so because it would much better match my PIAA super plasma gt's.

3) I put one in my turn signal and kicked on the hazards to compare with the stock rear turn signal bulb. The LED came with a little piece of paper warning not to put them behind any tinted plastic and especially not the amber automative kind because any color other than the native color will filter out brightness and amber + blue/white is the worst combo.

HOWEVER, it didn't look much dimmer than when it was behind the clear reverse light cover. But, it still was substantially dimmer than the stock rear blinker. But, the quickness of the off/on/off transitions were amazing. It just felt so "crisp" and no-nonsense.

Subjectively it felt about half of the brightness of the stock blinker and a quarter the brightness of the 50w halogen reverse.

According to http://www.luxeonstar.com/luxeon-emitter.html - the white luxeon only does 18 lumens while amber is 36, red is 44 and red-orange is 55. It is hard to say if the red-orange is orange enough to be used as a turn signal. But I think I am going to try some.

I think part of the brightness problem may be due to the directionality of the LED, even with a ~140 degree viewing angle, the housings just never "glowed" they way do with the halogen and stock bulbs. Perhaps stacking a side-emitting luxeon underneath one of these "lambertian" ones might help to give the light a more full effect.

On the other hand, a quick poke around on the net seems to indicate that a white 50w 12v halogen light should produce close to 900 lumens. I think our eyes see brightness on a logarithm scale and lumens is a linear scale, so the difference may not be so bad as it first appears.