I've owned this dimmer for nearly 10 years and I just replaced the incandescent bulbs with LEDs. The circuit originally had 4 - 65w BR30 floods and 1 - 50w PAR20 spotlight. The replacement LED bulbs are 4 - 12w BR30 bulbs by Luminus and 1 - 8w PAR20 bulb by BAZZ.
The dimmer seems to work OK with no humming. It steps all bulbs up and down with varying intensities but for some reason the 8w PAR20 bulb remains lit even on the lowest setting which would normally be "off". I can turn it off by moving the bottom slide switch to the left. I like the effect it creates. It is directly above my desk and acts sort of like a nightlight. It illuminates enough that I can use my computer.
I guess a 500w rated dimmer is not as finely tuned as a 150w dimmer which would normally be used in this situation.
Are there any negative ramifications to using this configuration?
As a side note, I have replaced all of the lights in my home with LED. This circuit doesn't cause any RF noise when listening to AM radio. Two other circuits with 6 - 12w BR30 bulbs each and "legacy" 500w rated slide dimmers work flawlessly and don't create RF noise either. I used an LED rated dimmer (150w) on one of the circuits and it creates RF noise. A couple of table lamps create RF noise when using dimmable bulbs (without dimmer) but are fine when using non-dimmable bulbs. So I don't know if it's the bulbs or the dimmers or possibly both causing the noise.
P.S.....Yeah, I know....AM radio? ...my wife listens to talk radio on the AM dial. I told her to stream it on her iPad if she didn't like the buzz LOL!