Yes, it works pretty well and the longer the period over which it needs to be dimmed, the smoother the change will appear. Chris added support for the transitions too (without transition support you would need to do a lot of calculations in scripts/automations in order to get the correct timings to send new values to the lights).
See below examples of service calls:
#turn on to 30% (previously off) or dim from any brightness level to 30%
- service: light.turn_on
#turn off (this service does not take brightness or other light properties but only transition, if specified); this would dim the light to 1 and then switch it off
- service: light.turn_off
What I forgot to mention previously: Milight bulbs turn on with the last known values for color and brightness and this might be looked as either an advantage or a disadvantage if the lights are bright or too dim (for comparison, Hue can either use the last known value or turn on with a default value).
In my case, in order to turn light off I chose first to set the brightness level to 1 and then turn the light off (I don’t use transition from off to a specific brightness level but only between different levels when light is on). As a result, when light turns on again it is at brightness level 1 and it won’t result in a short blindness as if it would happen when turning the lights to full brightness in a dark room. Also, case there is a power failure during the night the lights will turn on to level 1 when power comes back on and the chances of waking up are lower vs. full brightness (or last known level before turning off).
I use 433 Mhz, Z-wave (868.42 Mhz - Europe), Zigbee, Milight, Wifi (both N and AX&AC with only the devices not capable of higher bandwidth kept on 2.4 Ghz; in addition, there are over 20 APs accessible from the neighbors in both 2.4 and 5 Ghz bands) and Bluetooth devices and I haven’t seen major issues with interference except one related to 433 Mhz devices that affect HD TV channels from a particular provider (macroblocks appear on screen for 1-2 seconds when 433 Mhz devices such as motion sensors or door sensors fire in close range, however I haven’t seen it with the other major providers in my country).