I've just bought a Milight bridge, 9W RGBW bulb and 2.4Ghz remote. All from Amazon Uk (from sellers Datawize, BatteryLogic). From researching online it seems there's at least 5 different names for these bulbs (milight, easybulb, led logic, limitlessled, etc). The seller of the bridge/hub/controller/box/thingy assures me it's version 4 (there have been 5 versions) but I can't see how to tell without taking it apart.
I downloaded the android app 'Milight 2.0' by 'Sunny' which seems to be the official app. The instructions actually refer to 'Mi.light' app, which seems to look and work exactly the same (i.e. not very well). I managed to use the app to find the bridge by connecting to it's own Wifi network. You can then go into configuration and "AP configure" which allows you to join it to your own Wifi network. The inbuilt wifi then seems to turn itself off.
Now at this point I repeated the above steps several times, because I couldn't (or rather the app couldn't) see it after it had been configured. You can re-set the thing by holding in the hidden reset button with a pin until the lights flash rapidly.
I also at this point went into my router settings and made sure DHCP would always give it the same IP address (based on its MAC address).
After a few attempts I went back to the Play store and found the Wifi RGB Led controller app by Cold-Core which actually recognized the bridge and allowed me to pair it with the bulb (to do this, turn on the bulb at the switch and press "on" on one of the zones (1-4) within 3 seconds - the bulb will then flash 3 times for success. The pairing process is identical for the plastic remote control.
Now that all worked I configured the openhab binding by following this page https://github.com/openhab/openhab/wiki/Milight-Binding - substituting my newly assigned static IP address and putting port 8899 and using channel number 6 rather than 1 to reflect how the new bulbs/bridges work. I can now turn bulbs on/off and change colour both remotely and automatically (e.g. when home is unoccupied, or when i stumble downstairs in the middle of the night).
With that all working, overall I'm impressed - for a fraction of the price of Hue/Lifx they seem to do the job. The only downside I can see is they don't report status, so sending messages is "fire-and-forget". I haven't had any problems so far however.
There's some detail on development and versioning of the APIs, bridges etc on www.limitlessled.com/dev/