So first the basics: The keyboard looks good, is very ergonomically designed wireless connection via USB is convenient and always worked flawlessly. The special features I personally have largely unused, but a nice feature. The biggest advantage for me was the palm rest and the mentioned ergonomics of the keyboard, so typing is much more pleasant, so from my 4 stars.
Now a few cons: The key action mechanism is pretty hard, which is not necessarily bad, but it will be difficult to move with the times (ie over the years). So who is more interested in life or a soft typing feel, is better off with a Cherry keyboard for the same money. In addition, the gaps between the blocks are quite large, over time amounts accumulate dust and dirt under the surface and between the keys; Since then helps only disassembly. In addition, the "pores" and edges of the palm rest are difficult to clean.
Conclusion: For people with wrist pain or those who place great emphasis on writing comfort, this keyboard is just right. Otherwise it is just a Standardtastur Logitech wireless and other bells and whistles; are as justified because 40 is an open question, however, I would note that there already are quality Tasturen for a similar amount of money from Cherry.