Most of the time things don't work out as easy as shown on promotional videos from some hard-ware stores. But this time it was really not soooo difficult: dismantle the beams in the salon including all ceiling elements, pull in a new cable connection, rewire a few switches and then, glue the LED tape - done! Batsystem promises that the dimmer protects from over-voltage and only lets 12 volts through. Thus, the LEDs live longer, even if voltage fluctuations coming from the diesel-alternator or i.e. the anchor windlass.
Now there is LED lighting in the salon and it is actually like this: there is not only more light output and thus a better environment for reading, playing or doing crafts, but above all the feeling of space has improved. And all that for a ridiculous additional 9 watts. Dimmable and in a perfect light color for me.
I installed LED spots in the cabins too. Not only do they provide pleasant light, there is also a USB plug on the base, so you can charge electronic devices easily. Costs and assembly effort are manageable.