@frg Okay, this is interesting.
After reviewing your log, I have no idea why this message still appears. There are 7 incoming presentation messages, all handled before. After about four minutes after the last presentation message was received there are 7 warnings about already presented childs. I don't see that behaviour in my log.
It's nothing serious we need to worry about, maybe the category "WARN" is exaggerated for this message. I'll look for that behaviour in my system, so that I may be able to reproduce it, but at the moment I don't see anything I am able to do here.

@LastSamurai Thank you for the feedback!!

I'm glad RGBW seems to work.
RGBW status indeed wasn't working, that definately was a bug and is fixed now (for RGB too).

About your general questions:

You don't have to define the gateway in the things file. It is not discovered automatically, as this is something that is not very easy to implement (i.e. search for serial connections on windows / linux, search for network devices, is it a gateway or not?)
You may just use PaperUI: Configurations -> Things and hit the white plus sign in the blue circle and select serial or ethernet gateway.

When it comes to things and items: for me, a thing is a sensor. For example the RGBW sensor is a thing in the OpenHab world. There are a few channels (children) that are frequently found, when this sensor is used: one channel for RGBW, one for status and occasionally var1-var4 and battery. The thing is defined by its channels. The thing is a representation of the hardware in this case.
The items are the representation for the UI and the user. The user uses the Color picker and the thing/hardware needs a string (#aabbccdd). There may be "hardware" behind an item but there is no need to. An example is the lastUpdate channel/item. The information is not send by the sensor, it is generated by the controller/binding.

@strangeoptics SmartSleep is supported by the Openhab 2.0 binding.

@frg Please enter log:set DEBUG org.openhab.binding.mysensors in the karaf console and post the debug log of the binding here.

@edsteve Yes, that's one goal of the binding. For the serial gateway the hardest part is to determine the path of the serial port. Something like: /dev/ttyUSB0 or /dev/ttyACM0 if you're using Linux.

What exactly does not work? Please attach a log from the karaf console.

@FusedHe3 Please enable DEBUG mode in the karaf console and paste the output around Variable 2 not present here.

@RVMRVM Interesting. Do you have a corresponding log for me?

Here's my test:

[INFO ] [arthome.event.ItemCommandEvent:43   ] - Item 'mysensors_rgbLight_8a7ca179_rgblight_199_0_rgb' received command 71,46,91
[DEBUG] [.c.thing.internal.ThingManager:366  ] - Delegating command '71,46,91' for item 'mysensors_rgbLight_8a7ca179_rgblight_199_0_rgb' to handler for channel 'mysensors:rgbLight:8a7ca179:rgblight_199_0:rgb'
[DEBUG] [.m.c.MySensorsRGBTypeConverter:63   ] - Converting RGB Int to Hex: R d4, G e8, B 7d
[DEBUG] [b.m.i.gateway.MySensorsGateway:563  ] - Node 199 found in gateway
[DEBUG] [b.m.i.gateway.MySensorsGateway:567  ] - Child 0 found in node 199
[DEBUG] [ractConnection$MySensorsWriter:524  ] - Sending to MySensors: 199;0;1;0;40;d4e87d

Hey @doctor64 !

Please open a new topic. This one is getting really huge.

Please check if the temperature channel is linked. In PaperUI you may do this by moving to "Configuration" -> "Things" and click on the sensor data.

@RVMRVM The definitions carlyler posted looks fine and I've tried to implement this logic into the binding so you won't need the rule anymore. Feel free to test my binding or stay with the rule. Hopefully both would lead to the same result.

@FusedHe3 Thank you for testing and your input!

The sketch you are using is representing itself as a RGB sensor and the log you've posted looks good.

About the fiddling with the .items file and the color picker: Thank you! That should'nt be needed anymore, I've changed it here: RGB-Test-Binding