As you confirmed you had your gw / sensors running on 2.x I gave it another try and started from scratch, and wiped the eeproms on both my gw and node.
New Install of Arduino IDE, new MySensors Library install. I used the ethernet gw sketch example and a temperature sensor node sketch.
This time it worked, I was able to finally include the sensor, what I can tell from the debug output communication seems to be working flawless.
Even when cutting power from gw or sensor and powering up again communication is recovering.
Now I will work on adapting my old sensor node sketch on lib 1.4 to new 2.1 requirements.
Thank you so much for taking the time to help me get this going 
