I've just had a quick play with LEDIson after updating to the 1206 ROM, and it looks like although the software supports 255 brightness levels, the LEDs don't dim accordingly. A simple test is to create a sequence with one LED starting with full brightness, then duplicate the step, editing it to drop the brightness by 20 units. Repeat a few more times then play the sequence. The result is that the LED seems to flicker between steps but does not fade.