I have installed the motor controllers into the shield electronics( yes, it has finally arrived from oversee). Two cable short circuited so one of the stepper motor controller burst to flames, literally! ;) It had about an inch tall flame, what is pretty impressive if you see how tiny the chip is ;)
I was too eager to see the printer come to live, so I was rushing things and I didn't properly insulated the Z axis cables at the plug.
I had a few problem with the end-stops wiring, but I got quick help from the Reprap community. So I could fix my firmware settings inverting the end-stops. I would like to thank for them as well to recommend the RAMPS electronics the first place. Because if I go for Gen 6 electronics now I would have a burned out main board. But with Ramps I can just get a new controller, what is around £10 only. I did order two right away, just for being on the safe side. ;)
By the way, installing a main switch was a really good idea, I could cut the power in seconds, when it was on fire. Preparing an extinguisher is recommended, for next time. ;)