I replaced the front indicator bulbs for some 35 LED ones and they are great,however,I have black eyes on the car so I removed the orange plastic to clean up the look of the headlight.
just out of interest did you get a red LED bulb or a white one,and how many LED did it have in it?,I think the rear lights are realy bright on the MK3 I am always checking the fog light switch as they are so bright.
I guess LED tail lights are great if you have some lexus type lights which dont have the red plastic ,then everything looks clear but shines the colour that you want,but if you were fitting them in the standard lights then I'd stick with the standard bulbs.
The good thing obviously with the LED bulbs they should last for ages.

Darren